GT - Oil Temps in climb are usually the climb-limiting factor with some of the earlier Rotax. The later models use a larger "Earls" oil cooler which might help.
Becasue of the gear box, it's doubtful you will ever handprop. The compression on the 912S is too high anyway. join the S7 group on Yahoo groups and do some searches there - its been discussed quite a bit. A strong battery is a good idea. I and many others run the Odyssey PC680. It fits the stock battery box, has more cranking power (which the Rotax likes), and has been bulletproof for me and others
http://odysseybatteries.com/battery/pc680.htmYou also might consider joining the Rotax-owner.com site. Its a private site (not a factory site) and is paid ($29/yr), but has videos on all things rotax - jetting, carb synch, maint., reviews of products. It also has for free a lot of resources - manuals, location of qualified techs in your area, I think its money well spent.
And yes, jetting is the only way to control mixture. I have never touched mine, so not experience, but not hard to do. I think the rotax owner has a video on it I think.