Correct area to drill. Use a drill stop as not to let the drill bit go too far in & hit the diaphram while you are drilling.
You do not need a separate filter for the turbo,it was just a suggestion.
I am saying,, for you to start off with really low boost,, if you start off w/6 psi & your timing is incorrect or your A/F ratio is way off (B.T.W.,, it will be off) or both are way off, you can destroy your cast piston engine very quickly.
I am suggesting for you to start off w/1 psi, check for detonation ,observe your A/R ratios & proceed to make adjustments as needed.
Then proceed to 2 psi, listen & check (take out spark plugs for visual insp.)
Then adjust for 3 psi, listen for detonation, check your spark plugs, run 4 psi, listen for detonation check your plugs A/F ratios. Run 5 psi check for detonation, read your plugs. & so- on & so- on & so-on etc, etc, etc. http://www.nightrider.com/biketech/spkplghnbook.htm#In
You need to be on top of these things to check, if you don't take this boosted engine serious,,, say bye bye to your stock rebuilt eng.
You can have your timing retarded, not run much total advance , your gas mileage will suffer greatly, throttle response will be sluggish.
If you are not going to use an intercooler, no methanol injection, no MSD boost retard box, I would not run more than 4-6 psi range on pump 91 octane fuel w/conservative timing.