If I understand correctly:
In currently state this “BLF GT” driver with 12V/2,5A can run a xhp35 about 2500lumens, xhp50.2 at 3600lm, 70.2 at 4400 lumens (from Texas Ace’s charts).
The modified version of this with 12V/6-8A can run a xhp50.2 at maximum (5000 lm) , 70.2 at 8500-9500 lumens at 6-8A. Maybe kill the xhp 50 at 8A, and will it kill a xhp35 already over 3A? So is is not recommended using this high current driver with xhp35?
The drivers are build for the current you ask for, so its like you want 2A or 4A no problem to change that on every order
Just going over 5A needs better parts that add cost
Keep in mind those current numbers are for keeping a high efficiency, of course you can get more out than 5A of the original design, but the efficiency goes down and heat up
2S/2P carrier and 6V LED can be used with normal parts up to 5A with lowered buck frequency
with upgraded parts about 8A
of course this might be well enough for a XHP50.2, but rather poor for a XHP70.2
Those are the currents to stay safe well within specification of the parts, of course it is possible to get out more but then no guarantee to operate without any issues over a long time,
if you want it just lower the sense resistors as usual for buck/boost drivers
I made a 30mm layout that could be extended in my board program to the nessesary size or grinding down the 42mm TN42
The Curoi should be 38.5mm, if the edge clearance is small the TN42 could fit