Man I feel you on the furnace thing. Did a basement job last winter where the homeowner had one of those old forced air units and every time it kicked on my laser line would jump a quarter inch, drove me nuts. Went through the same deal, re-marking and second-guessing myself til I just said forget it and snapped a line. Chalk line dont care about vibrations or drafts or nothing, it just works. My laser sits in the truck now unless Im doing a wide open room with no air moving. Funny how the old tools still beat the fancy ones when conditions get rough.

Skip the manual tweaking and let the sweep find what you missed.

Yep, burnt rice is the worst.