I built a 20" DOB about 6 years ago as my first ever A) large project,
B) telescope project, C) wood working project. I suggest picking up
"The Dobsonian Telescope" Berry and Kriege and read it about a donzen
times.

I was lucky with my project, I was looking between a 20" and a 25" set
of optics, and the 20" optics set came into my hands first. After 6
years with this scope, I have come to the conclusion (for a varitey of
reasons) that a 20" scope is the largest scope a single person can
manipulate alone.

Budget about 10 times as many hours as your first plans call for.

Mitch