That came out great Mouse-nice work!
I had the same thoughts on the stanchion deals when I built mine but as it was brand new off the lot, my wife said NO WAY was I cutting a brand new dash... So, I built mine from some 3/16" plate and traced the dash as close as I could, keeping all factory functions able to still work-including the floor drain. What I did at the bottom was make the feet a wider footprint, then made a lower plate that is roughly 13" long which bolts through the floor and through my sliders in 3 locations for strength. Figured this was stronger/better idea that the single one bolt through the floor drain. It's seemed to work well. The other thing I did on the top plate for the dash pillars where it comes over the top of the dash and where the windshield tubes meet at on the flat plate-on the UNDER side of that top plate, as the dash is rounded on two sides, I welded in some 3/16" plate at roughly a 45 degree angle running both across the front side and the outside edges of the top plate where it's welded on the main pillar. What that does is take the roughly 3" wide top plate (or whatever it is) and with the angled plate underneath, transer load and strengthen the pillar top overall. (in theory anyway) The round tube when welded on then overhangs both of my angled pieces (underneath) theoretically for more strength-which you CAN'T see unless you pull it and flip it upside down. This would be an afterthought of course, but was another way to strengthen the setup. In my mind anyway. Works great.
Also noticed there was limited holes/cut outs in your pillars-good idea. I left mine solid and they've been fine. While I've never ROLLED my rig, it's been on two wheels MANY times in the timber and I frequently use it as a pivot of sorts like my slider bars and stryker rails. It's held up great with nothing more than scratched paint. I'd like to add the X and harness bar at a later date, but for now, it's worked well. Yours should be extremely stout and hold up very well just judging by what I've done with mine. Again, great job!!!
Best of Luck,
Mike