I would recommend you connect your light cycles to the light cycle insert lights just in front of the ramps.
Frolic's experience is the second report I've gotten on some odd behavior on Tron Pro's. I haven't been able to reproduce the problem, so it's been tough to trouble shoot. The problem does not exist on the Tron LE, and the problem doesn't exist on other pinball machines with similar light matrix systems.
I will be looking at a Tron Pro this weekend so hopefully I'll be able to reproduce and fix the problem. I will let you all know as soon as I can pin down what the problem is.