Ray,
You're right. I just replaced the canister with a spin-on PH8.
The restriction will be in the outlet fitting at the spin-on adapter. So the inlet line will have about 20-25 psi and the return line will have essentially no pressure. I don't think the PH8 has an anti-drainback valve, but 20 psi should be enough to overcome it. I plan on using a 1/16 restrictor that will allow about a quart per minute through the filter.
regards,
Leon
