All of the above posts make sense - the vaporisor should be too hot to touch. Might make me think about my coolant routing.
Just to play devils advocate though -
LPG cars I have had before (Range rover- mixer, Veccy SGI) have all fired up, and flicked straight over to LPG from stone cold :-/
The ad for the kit we have, also states "Start on gas".
32deg isn't good enough for a running temp in the vaporisor, but I'd have considered it's enough to make it run OK (when it's calibrated).
Might be worth having a word with Jeremy?
Out of interest, did you determine if there was a need to drill your fuel nozzles?
One of the guys from Nots who did a DIY LPG SGI, found that his car wouldn't run well because the injectors needed to be wider.
It does sound as if it needs "calibrating" or setting up, and if the software won't let you do that below 60deg, then you won't be able to do it. Stick the temp sensor wires on the CTS to temporarily fool it?

Other than that, it could be that there's not enough gas getting to the front - either a kink in the pipe (doubt, as you say it's a good job) - or the tank valve not letting enough gas out. There should definately be a manual shut off valve for gas, on the tank.
Hope you get it sorted mate.