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There is one way to find out 
Your amps will go down most likely, but the lumens should get a bump, and definitely throw if focused decently. It would help if you got the springs bypassed of course. You may want to work out something for centering. A few of us use the standard XML centering piece, and allow the XPL to catch it's ends on the XML piece - if you do it right, it perfectly centers an XPL or XP-G2 in a XML centering piece.
5 amps on that stock XML alum PCMCB is really stressing it - I've had those desolder themselves because lack of a decent thermal path. The copper MCPCB is a huge difference I keeping it cooler.
Do you know the stock MCPCB is 16 mm, not 20? I think I used 20's but you need to sand them down to fit. Take a look, and some measurements before you order parts.
Other than that, the reflector should be fine. There are some classic HD2010's that focused best with the pill loose, not tightened. If you got one of those, you may have an issue, maybe not - could loosen it to get a good focus with the XPL HI.