8' X 5' x 1.5' (18") = 60 cf 8' x 5' x 1.3' (16") = 52 cf cord = 128 cf
I'm sure you're way over a lot of sellers, but looks like you're actually a bit light.
18'' pieces only short you 6'' off the ends. The extra foot in height would just about make up the difference.
I cut whatever length people want. ~98% is 16", the only 2% is 12, 14, 18, or 24".
I put in short pieces. I just stack it together, so 2 ~8" pieces for example, or toss the piece on as extra. If I'm at the end of a log I'll usually make 2 12" pieces vs a 16" and 8".
I sell the drop offs as chunk wood. For a discount of course. It gets rid of my junk and gives people a cheaper option.