Brian, I think Hector meant 3 mins on compression in low gear, then change into high gear and get it spinning without compression then flick the compression and fuel on at the same time. I've never started one with the two-speed so have no experience to share. Seems like the pony should be able to spin the main under compression in high gear indefinitely - to be designed otherwise seems a little under-functional

That's what I'm writing - run it in low with compression on, not off. You need to build heat in the main engine, regardless of whether pony can handle high gear with compression on. Your statement about needing to run with half choke explains everything - you need to richen it up. Either you have a blockage, or your main jet isn't adjusted correctly. Just try opening the main jet up a bit and flick it to compression on.
So, the sequence is:
- start / warm pony
- low gear, no compression until pony is stable then turn on compression. Run for x minutes like this
- high gear, no compression, when pony stabilizes, turn on compression. If pony starts to falter, richen it up a tad. Repeat until success or you run out of mixture adjustment in which case we need to diagnose further

Check how fast the fuel runs out of the fuel bowl. Open it up and let the bowl drain fully 2-3 times the amount that the bowl contains. If it flow slows down appreciably, you're not get sufficient flow. The fuel level in the bowl needs a minimum depth for the jets to operate correctly - if the level is too low (.e.g. if the incoming flow is not enough), then you'll starve