12 meter element:
I made mine 221 inches. On my MFJ-259b, the SWR is very sharp 1.6 throughout the 12m band
17 meter element:
I made mine 312". SWR is 3.8 and very broad and almost undetectable in the MFJ259b.
It also tunes up great on 20 meters. I use an antennqa tuner to briing everything in to 1.0 SWR