I built the? Marcus one. Has been in service for over 3 years. As you say " Cheap and dirty " ....
Have never had to do anything to it. Is set for 10.000000 mhz. and stays there.
My freq counter? a DSI 5612 had a terrible time base osc in it. Was not accurate in any way.
Modified the counter with an OCXO osc on 4.0 mhz.
Now when it reads the GPSDO at 10 mhz is is dead nuts on .. Error is usually less than .2hz?
A great? "CHEAP " reference ..
Graham VE3WGW