First time Building my ownP60

You will be good to go with that setup…

You can easily run 8*7135 on an XM-L, but at 2800mA it will get pretty hot pretty fast

This link should help you out
http://flashlightwiki.com/DIY_P60

Expect that XM-L2 at 1500-1750mA to hit around 700-800 lumens
http://flashlightwiki.com/Cree#XM-L2

Another great thread you should visit