Ralph, it actually recommanded by the factory to use a Albright knot to attach fly line when using gelspun backing. It is great to use bimmini to loop on to the fly line when using dacron because it is thinker in diameter so it would not cut the line as easy but on the other hand, gelspun's diameter is too thin, and it will dig into the loop when tension applied and end up cutting it. By using Albright knot, it gives the line an extra layer of cusion becuase you actually double the fly line. Plus, if too much tension applied to the fly line the end result will only cut/ stripe the coating but not cutting the core. As you also mention about using kevlar loop, those thing are so big and stiff, if the fish is running fast to the backing like a tarpon, you can actually bust the guide insert even on some of the new fly line that came with a pre formed loop.
one other thing,the reason to use gelspun is to use the same breaking stregth backing but thinner diameter so you can store more backing. If you use 50 or 65 lb gelspun, its almost the same diameter as the 30lb dacron then why bother to use gelspun. Unless you want a heavier backing thats a different story but still, most fly line core is about 35lb and most class tippet is 20lb. In other word, your rod will snap first before the line. And if the fish is running that fast, that going to cut your hand, that whats the drag on the reels for. goodluck fishing