good writeups!
I make MBCs using a natural gas valve from Home Depot. they're about $30 total, $20 alone in the big valve, but much easier to use and more pleasant looking.
ill snap some pics later of the one on my brother's car. i still have a profec type s buti m ditching it in favor of a larger wastegate spring and an mbc since ill only need it to jump about 2-3 psi over wastegate pressure and dont need the high low, since i prett much run 15psi daily.