If I get one of the 42mm BSA red dots for just general plinking, will it be high enough to see through easily without using a riser of any type? This is roughly what my gun will look like.

http://www.olyarms.com/images/pcr16.jpg

There won't be a front sight to get in the way on this gun. I want to share duty between a red dot and a 4-12x44AO conventional scope. I'll probably ditch the whole red dot idea if it won't be mounted high enough, as I don't really want one badly enough to spend the cash on a red dot and a riser to mount it on. If I end up buying a riser to mount the conventional scope, I'd probably still buy a red dot, I guess.

Thanks for any info or experience you can provide.

I was wondering the same thing. I found a cheap 45mm red dot sight, and now I need a rifle to go with it.

I use an ATN Red Dot on my flattop.  It requires a low and tight cheek weld, as if there was a rear sight.  It 'co-witnesses' across the front sight.

I think the BSA would have about the same sight profile above the flattop.

FWIW, I have another reddot mounted to teh top of an A1 upper.  It gives a more relaxed 'head-up' sight picture, but both of the sight options work equally well.

TRG