Pro-grade equipment to manage pressure has filtered down to the homebrew and nano scale, and these two units will get you spunding with style.
Ss Brewtech Sspunding Valve Adjustable PRV
Two models offer varying levels of convenience—if cost is a priority, the non-scaled version will get you into the game safely at a lower price point. Or, splurge on the scaled model for direct pressure measurement and the handy quick-depressurizing plunger. For tanks over 3.5 bbl, try the pro model.