20 minutes is too short to use NP for estimating FTP. It will most likely be too high. If the hill climb effort was all out, snot on the bars, as hard as you can go, I'd use 95% of the AP. Assuming you had a pretty good warmup with some really hard efforts. Its worth noting that the 5 minute "blow out" effort before the 20 minute test is an integral part of making the 20-min test accurate.