Got Lindsey Racing Speed/Ref Harness

[exitwound]

Installed the Lindsey Racing Speed & Reference harness last night and I believe my car is actually working again. Started every time I tried it. I was down to about 25% success on a cold-start without wiggling the old harnesses.

My question is this: In order to install the harness with the engine IN the car mind you, I had to drop the new harness through the firewall through the big rubber plug the normal wiring harness routed through. I couldn't get the new harness down through that old harness hose due to lack of space. Now, I have the new wiring harness sticking out the side of the rubber plug on the firewall. Has anyone done anything to alleviate this so that the rubber plug will sit flush again? Right now, only half the plug is actually seated in the firewall and so I fear water/heat etc will get through the firewall.

With the engine in, and all wiring in working condition, there's so little room, I don't know how to approach this. Any ideas?