Autoflight recommends oil changes after 5 hours for a couple of times then stretching them out after that. The huge silting in this case was because of the cheap bearing.
One other owner has trouble with prop overspeeds for unknown reasons. I suspect it is the same problem, but no one knows.
I think this will not be a safe drive unit until an external pump and filter have been designed and added to the system. Without that you're just hoping nothing starts making fines between oil changes.
In most airplane engines, the oil filter is full flow, so only clean oil gets sent to the crank, then the governor and prop. Not so here. So the first hope is the governor pump has excess pressure available so you can divert the flow from the pump through a spin-on oil filter before letting the oil go to the prop hub. This is particularly appropriate if the prop hub is a high gain centrifugal filter. I have no idea if it is really good at that or not, and I have no idea if the governor has excess pressure available. Smells like a pretty big bit of instrumentation to figure out if you have excess pump or not.
Next way is rock simple but a partial flow filter. If the governor has a pressure tap or plug on the high pressure side, you can install a line to a filter and back to sump. It does need an orifice to keep this line from taking all the flow from the prop. If it only sees 10% of the flow at any moment, that means every 10 trips the oil makes through the prop, everything filter size and above gets trapped either in the filter or in the prop hub. Ok, maybe the regulator valves wills till trap some crud too. I do not know what the steady state oil flow while the prop governor is regulating is, but I bet it turns over the sump oil pretty regularly. If this filter removes more debris than the valves and prop hub and debris generation is slow, you may have a winner. .
The last way is to install an electric pump that draws from the sump, pushes oil through a filter, and returns at the nominal oil level. This too is a partial flow system, but even small scavenge pumps will flow a lot of oil through your filter, giving it a decreased opportunity to imbed, pit, or scrape surfaces and make more crud.
The filter should be a cleanable one with a screen of 25 micron or so. If you really want to get thorough, use two in series, one at 50 micron, and then another at 5 or 10 micron. The race car supply houses have a bunch of different sized ones that are low loss, sturdy and work great. Unscrew the caps, examine for fines, clean, reassemble.
With the separate pump, yes, you could add an oil cooler. Do you need one? If your PSRU sump is less than 200 F, it is a waste of money and effort plus more leak paths and failure modes. Above 200 F, and yes, a cooler might be in order. The higher the sump temp, the bigger the cooler needs to be, but with a goodly flow, any crud gets much less chance to imbed or pit or scrape surfaces...
Billski