Awesome thread with tons of great info.
I don’t have a RYTM but I do have some eurorack (without drum modules) that I sample for drums all the time. My mainstay for 909-esque kicks is a super fast exp. envelope modulating the exp. FM input of a thru-zero sine wave oscillator mixed with high frequency noise (also FM modulated by another exp. envelope) from a locked linear feedback shift register.
The hard part for me has always been timing the amp envelope properly so that enough of the low end decay gets through but not too much that it gets flabby. It’s usually a constant dance and tweaking game between the three different envelopes until I can find something that sounds good and has enough slam while still being tight.
Again, great thread, super excited to adapt some of the techniques described on my modular.