I would also agree that, for making larger bombers, using tubes is the way to go, because you can simply make them any size you like, and at the same time, thereafter add any size hook behind that tube.
However, there is no 'magic bullet' tube fly system;
Tying on tubes for floating ties means plastic tubes. It doesn't matter much whether that plastic is nylon, polythene, or another polymer.
What matters is, as you have eluded to, is how to hold that plastic tube in your tying vice.
There are essentially two ways of holding a tube in a vice: either the end of the tube is held in a Jacobs style drill chuck (there are many variants of this), or the tube is slid over a pin or mandrel and an interference fit between the outer surface of this pin/mandrel and the inner surface of the tube means that it won't spin during wrapping of your tube tie.
The best form of pin or mandrel is a matched tapered pin, closely matched to the inner diameter of the plastic tube you are using , and simply pushing the tube onto that tapered pin until it is tight (the interference fit).
As has been discussed & demonstrated in many previous threads concerning these matters on holding tubes on pins or mandrels, there is no need for the fly tying tool supply companies to provide dedicated 'system specific' pins or mandrels; why re-invent the wheel? There are already many tapered pins out there used for other purposes which can be co-opted for use in holding our plastic tubes: examples include the tapered shaft of a blind-eye hook, crochet hooks (come in sizes from ~0.5mm through to 10mm outer diameter), needles (eg darning & tapestry needles), the tapered pin sets which are used to expand ear piercing holes, and the stepped needles which are called felting needles.
As to holding the tube end on the outside, there are several different fly tying vices which are dedicated tube fly tying vices, eg the one produced by HMH. There are other vices where you can replace the standard jaws with a dedicated tube holding attachment like the HMH has. You can also take a set of very cheap pin vices with variable size collets (up to 3mm) which can be relatively simply and cheaply attached to a similarly cheap standard vice as a replacement to the original standard jaws. It all depends on your pocket, how much of your tying is going to be on tubes, and how innovative you are to make the minor adaptations to the already available tools which are already out there.
IMHO, the worst of all worlds for holding tubes is what appears to be the most common form of tube fly tying attachment which clamps into the jaws of your standard hook vice; these are usually supplied with 2 or 3 different diameter parallel steel pins with a brass bead or button on one end, where the user is expected to hold the tube by interference clamping fit of the tube ends between the vice and the brass bead at the end of the pin. Such a simple (and generally inadequate) tube pin system is the one most tyers usually complain that the tubes spin during tying; whilst you can adapt that smoothe parallel pin/mandrel to hold the tube ends more effectively (by adding a small section of silicone tube at either end), there are better methods (tapered pins as above) out there.
Mike
