Huh? Don't know about you, but I mod my bayo lugs by simply shaving the retaining tits down to where they won't click on the bayo, and you have to look up from the bottom to see any difference. Since I don't have a Fruedian addiction to knives, I'm not real concerned that it won't hold one.[:D]
Re the flash suppressor, you can either put a sleeve in the original, or use one of the A2 style muzzle brakes currently out. I sleeved mine, and of course pinned it.
Cost? Well, the A1 clone I built earlier this year cost me $325 for the complete upper assy, with all parts, and $275 for the DPMS complete current production lower, plus $15 for the A1 buttstock.
Where did you say you could get a complete SP1 for $615? [:D]
And if I'd had to have paid an extra $50-$100 for a special production A1 clone lower, bringing the total cost to $665-$715, wouldn't that still be $300-$400 under what a decent SP1 will cost these days?
Edited to add: Whoops, forgot the early type handgrip for $8