Graham - I've only heard about the malossi tops and that either they fail and/or eat cables. If you have a more detail description of where and why they failed I'm all ears. I'm hoping this design will take advantage of pa12 having a low level of friction.
PD- have thought about doing a small wheel or pulley inside to guide the cable; at that point I think its over-complicating something thats supposed to be simple. Personally I'd probably abandon the project at that point even though it would work.
I did a lot of testing last night. For about an hour and a half I set the carb up and just tugged the ever living shit outta that throttle cable trying to break it.
1. Pulling with a stupid amount of force
2. creating friction by going back and forth super fast
3. Pulling till full throttle and then slowly and gently letting it down and trying to get it to hang up or get stuck
4. Choke on. Pull throttle till choke off. Repeat 50x as fast a possible
All of this is over and over with different combinations of force, speed, and amount opened and closed.
And after all that abuse...NOTHING HAPPENED
Cable looked fine and so did the top. Never got hung up once. I feel pretty confident in this. My goal was trying to recreate an hour of heavy rally riding and see if this fails. It didnt and thats while being put under abuse its never gonna see.