Here's what I built for a light weight day frame. I want a minimal and more narrow frame to run shorter oars to hit smaller streams. I may eventually buy a mini raft to but this on.
1" EMT elbows inside chainlink toprail. Pins will be replaced by bolts when my stainless bolt order arrives. A 12", 1 1/4" sched 40 aluminum sleeve overtop of the side rails so I can use NRS oar towers.
56" wide by 40" long. I plan to sit on the boat thwarts and really just want a cage for the oars... but may add a simple flat seat if that doesn't work out. If I want to add cargo capacity I'll make a trailer frame using the same method.
It weighs 15 pounds without oarlocks and it cost me about about $60 Canadian (maybe $45 US) from readily available local sources.