DB Custom, the Nextorch SN50 looks like a Trustfire X7 clone, which has proven to be a great 4 x 18650 host when ordered with an optional extension tube for the XHP-35 HI. Check the mod builds under my X7 review.
I think 2.5A is said to be the sweet spot for the XHP35, so it sounds like you nailed it. Besides the LD-2 adapted for this emitter (and some of the larger and more expensive taskled drivers that are too large), is there another 2.5A buck alternative that will fit?