Yes, deeper sink rates to about 80 grains (10' T-8)
Then you can get that with an S8 Rio
Replacement tip 8wt (85 gr at 10’). Those are the same sink rate as t11. There are also s6 ones in the same set that are the equivalent sink rate of T8. The point here is that it is not total weight so much as the linear density that is more important for the casting. You may prefer the 7wt set (75 grains at 10’). For that set the s8 ones are either hard to find or don’t exist, but there are still s6 ones that are the equivalent sink rate of T8, so lots of options. You can test them out one tip at a time - no need to buy a whole set. Each sink tip in a set will have the SAME linear density and hence total weight for a given length.
Another tip is that (you can try it out for yourself) to get even deeper you can use a longer tip with the same linear density (grains/foot). They will be overall heavier, but will still turn over. The Rio
replacement tips come in 15’ versions and you can use them as is an they WILL cast, or as many of us do cut them back to 12-13’ to make them a little more manageable.
The take home message is the following: if you are using the t-stuff where all the tips have the SAME volumetric density (weight per unit volume) then yes, getting more sink rate requires more linear density (gr/ft), but it is not the linear density alone that determines the sink rate. For more delicate lines you have to keep the gr/ft down or the tip of the line will not carry the tip very well. This is why people who like to use tips with more delicately tapered lines tend to use compensated tips like the Rio
replacement tips. So I’d suggest what you want to try next is a set of 7wt or 8wt Rio
replacement tips. They will all have the same weight but different sink rates.
There are of course other options, not the least being steelhead style polyleaders. But the replacement tips are more durable and have a bunch of attractive qualities. Airflo makes some compensated (same weight, different sink rate) tips as well that have more of a taper, but the Rio
tips that come in at least 4wt to 10 wt currently do definitely have the most gradations to choose from.
The only “downside” is that these don’t come in faster than 8ips, probably because they would get too thin to manufacture. But 8ips (again approx. equivalent in sink rate to t11) and up to 15’ covers the vast majority of fishing situations. There are some folks that have well-argued the point on SP that if you NEED more than that you should probably fish somewhere else. At any rate when you shift even further up in sink rate (like t14 equivalent sink rate and greater) you will likely NEED to start using a skagit head. Yeah, I know, understatement of the week.
Hope this helps to get a little better oriented with/respect to the possibilities and limitations.