I just went through this on my Coronado 25, so I can at least talk about my solution. I believe the Quickstep and the Coronado are similar in that we have a "compression bulkhead" instead of a post under the mast. You are right not to want to drill through that.
All of my mast power wires exited the base of the mast, through a tiny hole in the mast step and into the cabin. I agonized over a deck plug for power and signal connections, and in the end abandoned the idea as extra clutter that I don't need on my small boat.
I simply used a hole saw to widen the hole in my mast step wide enough to accept the coax and extra power wires for other accessories that I added to the mast. I lined the hole with a plumbing fitting bedded in 3M 4200 sealant to protect the deck core from moisture. I've had some fierce rains and I haven't had a single drop enter the cabin through this fitting.
All of my mast power connections are in the cabin, secured to the overhead where they can be easily checked and maintained. In my case, I was able to run the coax to the port side, and through the existing wire run hole in the bulkhead, back to the VHF. This is below the compression bulkhead, through the regular bulkhead that separates the main cabin from the hang-up locker and head area.
I would think you can do the same.
S/V Old Shoes
1973 Pearson 30 #255