I have recently upgraded my UN1-027 gearbox as I have highly modified the engine and blew the 2nd gear syncro twice now,
Installed the Quaife replacement gear set, already had their limited slip diff installed previously
I did run into a little problem with this upgrade, I installed new syncro's yet again, just for the hell of it and got burned ... The syncros were aftermarket and seemed to work well going up the gears but would grind all the way back down, after pulling the gearbox out again and examining the syncros I found that the coating on the back of them was not the same as the Lotus ones, so I put my old ones back in and now everything is good again
Regarding the shudder effect pulling away from a standing start in 1st gear, I too felt this and it was not fun to experience, so I pulled the gearbox out again and replaced the flywheel and dual clutch, but the shudder was still there !!! :/
Next I replaced the gearbox mounts and added a new rubber coated washer to the passenger side mount as I noticed the gearbox does not sit completely flush on them, this cured 99% of the shudder, for me anyway
-Marcus