ive bin makeing these U/t test stations at work lately.. and since im the fabricator, i dont always get to cut and weld metal..
Ive bin makeing them outta 1/2" thick lexan.
i dont think you have a mechine shop in your bassment... but if you had a bridgeport. you can mill the edge's down, i use 1/4-20's counter sunk...... (the 1/4-20's are also plastic) bevel the sides and corners (in and outside edge)
then what i do is put a small bead of silicone on the mating surface (centered)
A few times i tryed dowl pins but that turned out to just be more work.
push it togther... align the holes and screw it together... i torque em to about 25lbs even..
give it 24 hrs then i come back and run a small bead of silicone with my finger over the inside corner (thats called a fillet weld (90degree angle)
for about 200buck ive made the Co a few 500+g setups.