I would lean-trim and roll with a wet-to-dry smoke chamber for moisture retention in the meat if it were me, but I think if you lightly trim the fat-cap and then cross-hatch score it should be fine. It will bulk up quite a bit as cooking progresses due to shrinkage. I would probe after a couple hours in the center of the packer...that will give you an average temp of the flat from end to end. The point will gain some more thickness from shrinkage so it should be probed as well, after the flat reaches your desired temp (point will always lag behind on IT because it it is thicker, unless you find a hotter spot to lay it on the grate).
Should work out fine...I had a 7lb packer from a case purchase a couple years ago, and it smoked up just like a 15lbr,, only I did change temps for the smaller brisket. I would start at 225* to pasteurize the surface for about an hour, then you can drop back to 210* or so to slow the cooking down...but there are some who say 275* works for them with an average sized packer, so 225* all the way for little guy probably won't hurt a thing. I'm a low & slow brisket smoker, myself, so I'd drop back the chamber temps a little after start-up...just me.
Separate the point/flat as needed to get the point finished without over-cooking the flat, of course.
Eric