I don't have an XP-50 but I do have a DR-5 and have done something similar to this in the past. I have to say I don't know whether or not the XP has a sequencer. If it does, follow the instructions below and if not just get your drum groove playing on the DR-5 and jam along on the XP. There should be no drop outs or skipping beats.
First you'll want to record your drum pattern in the DR-5. Then you need to connect a MIDI cable from the MIDI out of the XP to the MIDI on the DR. You then need to go into the MIDI menu of the DR-5 and select EXT. Now when you hit play on the XP sequencer the DR-5 will play along at the same tempo.
Hope this helps.
Stray