Chris, from my understanding, 1W EIRP on 137 is gargantuan.
Using the VK1SV calculator - the Hafler P3000 at 400W TOP is <500mW EIRP after going through the variometer. That places the voltage ~17kV.
Nice thing about that is that the corona arcs self-prune the adjacent foliage. LOL!
Antenna work here is ongoing - but as you would expect, the increments of progress are small. I'll be back on Tx in a few weeks.
Jim, WQ2H / WK2XAH