If OPS is being started before OMVS you can set USSMIN and USSMAX to 0 at OPS initialization (in the OPSSPA00 member) and update these parameters later after OMVS completes its initialization. You can create a message rule that intercepts the OMVS initialization complete message and uses the OPSPRM function to update the USSMIN and USSMAX. For example:
a = OPSPRM('SET','USSMIN','1')
a = OPSPRM('SET','USSMAX','2')
The only concern is if you recycle OPS in a non-IPL situation you need to check if OMVS is already active to reset these parameters in this situation as well.
Another option, in case you have OMVS under SSM control, is to create an UP_UP match action to reset these parameters. This way they will be set to their desired values every time the current and desired state of the OMVS task reach the UP_UP state. This will occur also during an OPS-only recycling as the SSMSTATE rule will detect OMVS is active.