Hi Parfittron.
I have not built the PSH-1, but did an earlier variant, the
PRS-1TS (no longer available) and my neck angle worked out fine without any alteration to the heel or pocket.
However IIRC, there have been a couple PSH-1's built here recently, so hopefully one of those members will advise more specifically.
re: the Gotoh 510 - I'm fairly confident that the existing holes will be fine for the Gotoh bushes with no need to plug & re-drill anything.
I installed a Gotoh TOM on my
PRS-1TS using the factory holes. Both the kit posts and the Gotoh's are an M8 thread so they would be interchangeable. eg: the Gotoh posts will fit into the kit bushes if needs be.
Hope that helps.
Edit to add:
One mod I made to my build, which I should have done during the initial build stage, is I added a scallop to the lower horn (more like a PRS). This made a big difference in the playability of this guitar as well as how I felt about it. At one point I was considering selling it without hardware as a project for someone else. Now it's a keeper.
Just thought I'd mention it for your consideration since you've not started yet.
Here's my before & after:
