Re: Construction advice needed...
I built one last year with standard 3/4 inch oak scraps which were littering my workshop. Plenty strong enough using biscuits, deck screws and tightbond III glue. I used 8 frames, 4 high by 2 deep, with acrylic faces on either side. Free standing on a 1x6" plywood base. Installed four frames from a nuc. After about 6 months, the bees are still going strong, but have very little honey stored due to our prolonged drought in Southern California. I would recommend having some way to supply syrup. Not so easy to add a frame of honey!
On mine, a feeder port was built to the base and I have used 1:1 syrup about 25% of the time, based on the amount of nectar and honey observed. I haven't yet taken it apart to clean the acrylic--make sure the observation glass is a bit tighter to the frames than is suggested in most of the plans to avoid wax formation. I'll have to break it down soon, since the top board is cupping badly due to the moisture from the hive, though the bees don't seem too interested in leaving through the gaps. Next time I'll seal the wood with more coats of linseed oil.
9 months, 12 colonies, TF (so far)