I am going to build for home, a broom wade ac25 type that has unloaders on the heads have it with a timed unloader solenoid in the pressure pipe to aid with pressure start up. Then as it gets to about 100psi ish (will have to check this point with clamp on ampmeter) currently (pun?) at about 15A ish at 130psi then have the unloader valve kick in to the one cyl furthest away from the fan, hopefully the load on the single phase is virtually halved and let that one cyl pump it up to 150 psi for air gun pressure.The heavier flywheel and 'missfire' will help achieve the higher pressure, but when blasting etc the pressure is maintained by both cyls. Yes there will be a little imbalance but I have known these run for years before someone has realised there is a lack of air flow capacity because a valve has gone down. In one of my workshops we inherited the comp and thought it was just asthmatic, turned out the unloader valve had seized on one cyl it probably had run like that for 10yrs! I have just built a petrol compressor from an old ac/pc 7 it is great max 160 psi and now with a ten psi differential you can hardly hear the difference unless the engine is idling (for less noise) I am over reving the pump at max rpm a little but it doesnt seem to complain at all, I just drain the system leave the drain open to start and then tighten up the drain after 30sec which lets it drain the air/water and warm up. i guess it is worth £500 if it was new it, cost me £15 for the bits and a donated chinese honda from a water pump. Very handy bit of kit. also handy for tagging in to system increasing overall cfm for blasting. might get the neighbours verbally blasting though.