I finally decided that Hoya piestolepsis had to be one of those few Hoyas that simply will not flower under constant day length. It had been under continuous 14 hour days since I had it so it was time to do something differently. I moved it to another tent where the lights were on for 12 hours each day. It stayed there for around 10 weeks and nothing changed so I new that decreasing the day length was not the answer. I moved it back to 14 hour days, and presto almost immediately the plant started to bud up, not just on one peduncle, but on at least 15 peduncles.