You're right about deraking the front end shortening the wheelbase, my ty250 has had that done & is about 1 1/2" shorter that standard which means it turns really well but meant the shocks had to be moved forwards to get everything level.
I need to work out where to cut the swing arm to add in 2" to get more weight on the front though as even with a sick motor it's prone to trying to loop
You need to use fairly soft shocks to get good grip, betors from John Cane @ TYtrials are a good starting point & are what I'm running now
The WES rear muffler has no restriction at all, they weigh nothing & from memory a wire passes straight through. Not really sure what the RL centre box is like but the standard ty 1 weighs a ton, the long header pipe is the key to the right power delivery, even the modern bikes have a fairly long 1
Sounds like a very interesting project which I'm sure you'll keep us updated on