So what happened to the final pictures?
I'm going to do this as I really dont like the high cross rails, mostly cause I'm 5'8"! The lower to the roof the tray is, the better.
However after having factory roof tracks on my R50 Pathfinder and doing work on those, I am very seriously looking at installing blind rivnuts and using hex or torx drive countersunk bolts to fix the track to the roof, rather than pop rivets. I've seen too many pop rivets pulled out, and M5 8.8 grade high tensile bolts will strip the threads out of steel rivnuts before they break, and there's no way a M5 rivnut is coming out as easy as a 3mm pop rivet. The harder you tighten them up, the more they grip.
And my Pathfinder tracks are bolted in this way, so factory fitments do it like this, can't be too wrong.
If anyone wants cheap steel brackets, get Land Cruiser 120 brackets from 4WD Supacentre or MCC 4X4. They work fine on the track.