Hey Pete.
Congrats on the shop build.
This is just about the size I want to do someday.
I was thinking a 35x45'.Just to be able to put pallet shelving on the back wall and still fit 2 trucks front to back.
And if you wanted to,2 more trucks could be stuffed in the center.
_Ogre makes a lot of good points .
I was a carpenter for 10+ yrs so I would vote for a stick built building.Shocking right !
You are on the right path.
If you ever think I can help,drop me a line.