You take twice the time to prefab THE perfect copper manifold for both the supply and return, being sure that not one drip of solder is visible, all lines are parallel, measure every piece so that it's both perfectly symmetrical and tightly spaced, tweak the circ flanges jjjuuuusssst right, you prop it with "gunners", then begin drilling for the F&M's.
Turns out the foundation has more rocks in it than an asteriod, You're 30 miles from anywhere without any lumber in the struggle in one spot...relocate till the next, slightly higher or lower spot will go deep enough for the shield.

Beautiful shiney new copper looks great...just not quite so with F&M's staggered slightly irregularly.
Next time, I'll bring a 2X4 and tack it up first....gggrrrrr.