When I switched to a Reflex front boot, coming from 10+ years of skiing Radar double boots, I ended up with the Radar HRT.
I didn’t like a full rear boot in combination with the Reflex front.
(First I couldn’t get the boot spacing right, but more importantly, I didn’t like that setup from a safety perspective.)
I couldn’t make an rtp work, tried a few different models but felt totally out of control.
The Radar HRT gave me the stability of a rear full boot and the mobility and safety of an RTP.
I still had to space the boots a bit larger than I used to, but there’s no way around with the Reflex release.
I took a couple good crashes with that setup over the years, but never had an issue coming out of the HRT even though I pull it very tight when I ski.