Yeah, I eventually got that setup and working, although it took multiple tries on OSX for me. I played around with it a bit, but I'm still a bit wary of the somewhat convoluted process of assembling the resulting app, mainly because I haven't fully wrapped my head around it yet.
I've been messing with
mpw a bit as another way to do classic mac development on modern systems. It doesn't have the modern features and native compilation speed advantages of retro68, but I also have a little more confidence and familiarity in it running the original MPW tools in emulation.