Good point HOSS.
If you go out on your own with little fuel (ie light) and set up a stabilised auto at say 60 Kts and note your RRPM and ROD. Say its 92% and 1800 fpm.
If you then load it up to MAUW and set it up again under the same conditions, and then use collective to bring the RRPM to 92% as before, you will notice your ROD will be very close to before.
As an aside, after doing lots of autos with students in the R22, I realised I'd never actually done one alone and light. Out I went and it felt very similar in the descent. The noticeable difference was that it was much easier to pull it up and land at the bottom. Less weight = less energy required to stop the ROD. Solo students, have a little faith....