Ok, so Adorama finally delivered that Flashpoint R2 SP trigger, thus far seems to work just as you'd expect. I connected my Takumar 50/1.4 m42 lens to the K-1 and placed the trigger on the hotshoe. I selected the right group and channel and set myself to Av mode. What struck me as immediately different to any of the other times I have connected a trigger (cactus) or using a flash in the hotshoe, was that I wasn't being 'locked' to 1/200 in Av mode. It was still behaving like as if there was no trigger connected 'up stairs'. So I could pan around my house and see teh shutter speed drop to 1/60, 1/30, 1/180 etc and it would still fire fine.
When going outside of course anything above 1/200 and the flash didn't fire (to be expected), but at least the shot still took, just flash did not contribute.
I can see myself having fun with a lot of manual focus glass, my intention would be to use Av mode indoors for events, and outdoors for HSS I would likely just use X Mode (which locks in 1/200) and then control exposure with aperture and/or ND filters.
I invested in the Xume system some time ago both in part to predicting this manual focus glass + HSS thing but also for landscape use;
The intention being to just quickly be able to pull a ND filter out to help with aperture control when shooting at 1/200 (allow for wider aperture shots outdoor).
Anyway, thus far I'm happy. My only gripe is that it's quite heavy once you have the AA's inside, and it 'wobbles' a little even when tightened on because not all the pins are falling into the holes in the hotshoe etc.