My 1st build was a 3 string fretless. I can't leave it alone. I have been playing for 30+ years and have a stack of "production" guitars. The Screaming Axe Handle is all I have played for the last 8 weeks or so (I may have 45 minutes on my factory made guitars in that time). I finger the notes and play a bit of bottleneck on the axe handle. I am putting the finishing touches on my little one handed nephew's Stogiecaster 4 string lap steel and his prosthetic bottleneck. I've played it some and like it pretty well too, but it is set up JUST for slide.
My next cigar box will be a fretted 4 string....that's the plan at least.
I bought one of Old Lowe's brass resonator cones a while back. I jokingly told him I was thinking of a Lexan body to show off that beautiful cone. Old Lowe, if you see this... I bought Lexan today.
If it turns out ok I'll post some pics. If not, I'll gently remove that brass work of art and stomp the rest. Lol.
As to your 3 or 4 string dilemma? You are on your own. I chose 3 because it meant I got to play slightly sooner.
I didn't mean to write a book. My plan was just to shoot you the last line. Sleep deprivation makes me wordy.