Made a few changes:
Went back to the CF TVPs and hand-made (in other words, not super pretty) a new center brace/motor plate combo to use the Flux mount with my 1521. The Flux mount's thickness reduces my gearing choices slightly. I wanted to use the Tekno mount (even had the holes for it in the old plate) but never got a replacement for the ill-sized one I received.
Also changed to an RC8 center diff:
Finally got a body painted and mounted. It's a Crowd Pleazer for a LST. It's funny, after 24 years in RC, I still can't paint for the life of me
and the mandatory "my daughter's excited about daddy's toy" shot:
The 1521 is definitely better suited for this than the Hacker XL. It's a heavy truck with all that battery. Can't fault the Hacker, though. It did very well and hopefully will be put to use in a custom truggy I'm planning on.