I wouldn’t replace 2 perfectly goodvacs to get more vac power, I would wait until they need replacing.
Funny enough I was going to start a post on increasing vac power on that CFR500 that I bought from you, i’ve Had it fixed and might start using it but I noticed the inlet port is very small, although it fits a 1:5inch hose the internal diameter is reduced. I’m going to make a new lid with a full 2 inch inlet so I can use 2 inch vac hose.
Are you using 1:5 inch vac hose? Maybe increasing it might stop restriction and give you extra vac power