People often make a really huge project out of strongback building. If this is what you enjoy, then by all means persue it.

I use 2 -14 ft. 2 x 4's made into a "T" beam. It's extremely strong and rigid and very little cost and work. Find the straightest ones you can find. I glue and nail them together using those hardened twist nails. Once those twist nails are in, they never loosen or come out. I have had mine for many years and many boats and I'm using it agin right now.