Those sorts of holes to the upper chamber are normal: in all the examples I have here they are much larger than yours. They are a rather random size. They provide an exit path for upper chamber pressures to reach the breather tube in the middle of the top of the cam cover (pointing back toward the back of the engine).
If you're getting lots of oil in your catcher, I'd have a couple of questions to ask before offering a possible cause:
1. What kind of oil are you using? If yours has detergents in it, there's your answer. Never use oils with detergents in this engine: they foam, causing lost oil pressure and roiling oil vapors thru the whole engine, making a mess. It also eats the crankshaft bearings.
2. What is the piston-to-bore clearance? If it is more than 0.0012" with a normally-aspirated engine with cast (not forged) pistons, this makes for oil escape past the rings to the combustion chamber. In a turbo'd or supercharged engine the piston-to-bore clearance should be considerably tighter, like 0.0006"-0.0008". If you have forged pistons, which require increased bore clearance because of their heat-holding ability, the normal 0.0022" clearance those piston-makers recommend will always cause blowby in these engines, I don't have specific advice on forged pistons with turbo/huffer engines, as I've always used cast versions instead - to avoid the blowby problem.
There are others here, though, who have successfully made huffer engines: maybe one or more of them will chime in with their fixes.
