Batboard

Hi. About the crosband repeaters I work a lot of time. I know how to do the GR300(uhf) with GR300(vhf), but now I have a new repeater which is a MX800 and I want to do a crosband with a GR300. MX800 is something wery new for me so I'm doing a lot of reading and testing on that repeater or base station.
Appreciate for any info.
Best regard.