A lot of questions!! Help!

[YEMX]

I've been talking to Motorhead and Milo74 via PM, but I thought I'd post this on the forum so I could get more input, and possibly help others who might be trying to go the same route.  I don't think I'm wording the questions right, and more heads are better than mine- I don't want to frustrate them. I have two projects I'm working on and need some help.

Prod90:  I want to put a Prod into an airsoft P90, and keep it a .22, but there's a few questions.  I'd like to reduce power to 12 fpe, and reg it with one of Milo74's regs.   I'm not using a gauge and need to drill a vent hole (I've been talking to Milo74 and I definitely need to drill a vent hole)- One way is to just use a factory main tube w/o a gauge (this would be much cheaper)- would that work to vent it?  I'm still using a gauge block, so it should be sealed fine (right?)...  If not, the other route I would take is to have a new main tube made w/o a gauge hole, and drill the needed vent hole.  But here's the big question for both routes: Since the Prod is going to be inside the P90 stock, how much area around the vent hole do I need to properly vent the reg?  Would I need to have the hole in the stock drilled all the way through the stock, or would a 1" (or more?) depth hole from the vent hole in the main tube be alright?  Did I word that right?  Also, thoughts on a LW hammer?  I'm not doing any valve mods, as I want to detune it- I am just going with a smaller TP size (.068") to restrict the air flow.  Thoughts? 

Discovery FT rig: This one is a .177 build and I'm using a Mrod trigger kit from Norm, and the kit uses a modified Prod hammer, w/the stroke adjuster.  Thoughts about what psi to have the reg set to?  I was thinking maybe have the reg set to 1500 psi?  Should it be more?  Less?  Again, no mods to the valve, just a smaller TP (.070").  Also, as this main tube I'm using won't have a gauge hole, as it's a custom one from Don Cothran.  I will also need to drill a vent hole- I'm drilling it on top, since there will be more than enough area to vent to (I'm using a BNM breech, no shroud).  Do I still need to use the gauge block as a spacer between the reg and the valve face?  I want to make sure before drilling any holes in my new main tube!!  Thoughts on what hammer spring to use?  Would a stock Disco spring work for this application?  Maybe a 22xx spring?  I'm not sure.  I'm also kicking around the idea of using a light weight hammer from Motorhead as well.  Thoughts?