secondary screw location
Usually - on most manifolds there is nothing in the way below the carb. But...it is often very painful to get on the screw with a driver (regardless of the type of head you install) from the bottom due to heat and other obstructions.
A fellow showed me the "hillbilly" way and I've used it ever since. Replace the screw with a longer fully threaded one - that sticks out far eough to tweak it with needle nose pliers. Doesn't have to be way too long - just enough.