Built the tiger 60 kit a year ago.
Quite frankly, I prefer the trike landing gear vs. the tail dragger. Tail dragger just doesnt look right on this plane, but thats a personal choice. Guy at club has tail dragger club and he seems to be Ok with it. I added Dual strut nose gear on mine, which perhaps is one very big advantage to a tail dragger, you get to avoid the dreaded nose gear blues. Rudder mod sounds Ok, but its hard to imagine it could be even larger. My kit built very tail heavy ( others had same experience, pehaps arf is different), had to add a lot of weight to nose. I like the larger tank idea but would suggest you try to locate it as far forward as possible, assuming your Arf needs nose weight. I have an inverted OS 70II Surpass 4 stroke on mine. No problems with inverted engine (with stock tank and placement). In fact, that engine was made for that plane. A OS91 would make this plane perhaps even better. I added a dubro fuel filler cap on my fuel tank cover ( in hindsight I'd have added it to the side, fuel cover blows with engine thrust). FG cowl seems like overkill, since you could "ply-in" the cowl for more of an inclosed look, but once again, if it adds nose weight and you need nose weight, why not.
Look forward to seeing the finished product. Good luck, This is one great plane.

Wayne
.