Yes, please let us know which forge Spike's uses or prefers. From the previous posts it would appear that the Cerro Forge (keyhole) is the norm for Spikes. I just finished my first Spike's lower build, it went smooth and is a VERY well cut and finished product. BUT, it did not fit well with an Anchor Harvey forge upper (splintered A), way too much slop for me. I don't really care about the color, but I insist that all my builds have a tight upper to lower fit. A great example is a RRA lower with a Bushy (keyhole) upper, you have to dremel material off the rear lug to get the two halves to close, that's the way I like it. I know that manufacturers and builders cannot do business this way, but us small guys can.
To answer a previous question, the "greek E" is an upper receiver made in Europe for Cerro Forge (keyhole), they started importing them due to the shortage earlier this year. I would assume they are cut to the same Cerro dims. But I don't want to find out the hard way, so that's why I'm asking if anyone knows what the tightest fitting upper is for the spike's lower. When I get home I'll pull out a couple of Cerro's (keyhole) and Cardinal's (bird head) and see how they fit on the Spike's lower and report back. Thanks.