It is quite known in the Spey circle you can use lighter-weight Skagit bodies as Scandi drivers. They have enough weight at the fly end to turn over heavier tips and flies than most Scandi bodies. The advent of FI3 drivers has been a boon in getting depth while using lighter tips and less weighted/ clunker flies; both necessary for smoother and faster unrolling of the front loop. This affords us to fish with lighter gear than in the past. Almost all my custom lines for my faster action rods are based on this approach.
I Scandi cast even for winter. I try to cast with the longest rod possible, where the long rod can help in raising deeply sunk flies as well as slowing down the swing. I bring a shorter rod on my pontoon as a backup for shorter distances if needed. Or sometimes you bring two-line systems for one rod.
I find with commercial solutions, I often have to increase weight class to have greater depth. Just think of the depth of T-8 vs T-11 along with their respective drivers. I find I can bend/ break this heavier-line, deeper-depths dependency. If you are willing to get into what makes a rod-line-fly system work (or not work) for you, you can find uncommon combinations of drivers/ tips/ flies to break out of the mold.
I just want to share some of my usual approaches. To some, you will find this complicated and messy; but to those willing to venture past the fixed walls of commercial solutions, read on:
In no particular order, changing any of these will affect the required line functionally and aesthetically (smoothness of flight):
1. Rod action,
2. Fly weight and bulk,
3. Depth of swing in given river speed
4. Dee loop clearance to bank obstructions
5. How far you need to cast
6. Class weight (the lighter the better)
7. How limited your casting style can work different actions
#2- The fly:
I often start 2 and 3 (what I think the fish needs for a hookup). Because I have a preference for lighter class weight rods, as well as for the efficiency of Scandi Single-spey from hang-down (esp for winter fishing), I like to design my fly to sink fast, easy to raise at hang-down, and almost weightless for casting smoothness (the exception for a lightly weighted cone that also protects the fly threads from unraveling). Without this first important step, you will have to go to a heavier weight class which defeats my initial preference. The fly I use is a 4-6" rabbit strip tied on to a 0.3" tube, where the hook trails past the strip on a knotted stiff Cameleon mono to minimize fouling.
#3- The Depth:
Because of the lighter-and-less-bulky fly, I can get away with lighter weight tips (and thus lighter drivers). However, my experience with tips is the heavier tips sink faster for the same sink rating (such as S6 sinks faster in 10 weight vs. 7 weight). However, this lighter tip buoyancy problem can be overcome by using a combination of a multi-sink driver, as well as a 2D sink tip as such: For my 14' Scandi 8/9 rod, I end up (from the fly end back) with 6' of T-8 and 6' of T-11. The T-11 not only turns over the T-8 section with greater authority and smoothly, but the downward pressure from it also drives the T-8 to sink faster (than if it was by itself) and into the slower currents in the lower 1/3 river column. I am hedging I am in a river speed where the T-11 section will swing in the faster current in the mid column of the river, which then minimizes the T-11 section hitting bottom before the fly.
1, 4, 5, 6, 7- The Driver
: The required driver is further influenced by casting conditions (4,5), caster ability to work different rod actions (7), and what Rod action and the weight class you want to work the river with (1, 6). To properly load the rod, Faster-action rods would require drivers whose balance is closer to the rod tip than Slower action rods. But this also means, there is less mass near the fly when getting enough loop speed, and this is where Skandit designs work better (although clunkier than Scandi). For the above 14' Scandi rod, I use a 34' 480 grain HI3 sink head from LTS. The total length including the above 12' tip is short enough for single spey without roll cast but long enough to not blow the anchor when going for distance. I can fish almost 95% of the runs going down the river on a pontoon. For greater distances using the same rod, I use a 425 grain Rio
Flight driver (cut back to 20') and attach a 30' section 1-2-4 (Guideline shooting head for single hand 8/9) as the tip.
I have a non-fast action 18'2" rod that requires a driver that is both long as well as near level taper in balance (it has a very slow taper). Although it bends deep it also recovers fast. 7 (how limited your casting action is) can often preclude staying away from slower action rods, which precludes long belly drivers, some as long as 55'. The benefit of slower line tapers is you are ensured there will be more mass near the fly which helps turnover (somewhat, the loop rolling speed is often slower, thus it is a fine balance between enough mass and enough loop rolling speed). However, if you have the casting range for longer rods, the options open up fast. I have used the above 425 grain Rio
flight driver to drive 39' of a 3D F-I-3 full sink head as a tip, giving me a total line length of 59' for a 16' McKenzie DTX rod.
So, there are many unexplored combinations to solve the fishing/ casting/ preference problems. If you are armed with the right understanding, you are armed with many pathways that can not only solve problems but also bring in more fine-tuning that, when added together, can make a big difference especially on the day of 1000 cast.