Sounds like you are making good progress on your projects. Keep us posted.
Battery (or perhaps batteries) will go behind the seat-back. I intend to install at least one of the EarthX LiFePo batteries. The LiFePo are much lighter than the standard lead acid battery with better cranking power. The EarthX version LiFePo contains electronics that protects the battery from any adverse voltage situations, so it becomes very difficult to damage it under nearly any circumstance. The Jabiru is lighter than the O-200, but I have mounted it a bit farther forward using the same mount that Paul Spackman has, so the moment is about the same as the O-200.
About my engine. I actually have a Jabiru not a Camit. Although the Camit was a very close version of the Jab, and by all accounts, better. They (Camit) have now gone belly up and all of their manufacturing equipment has been repossessed and sold at auction last month. I am not sure what the future portends, but there is always the possibility of a Phoenix moment for Camit if some of that equipment ends up in the right hands.
With respect to my engine. Jabiru is still in business, so the engine is marginally supported. Basically, the Jab is a well built engine, but is not as robust as the typical LycCon, so it is not a "set it and forget it" engine. With appropriate care, the Jabiru is a solidly reliable engine.
I have made some mods to mine that will add to this reliability. The only Camit mods that I have incorporated are as follows: I replaced the early hydraulic lifters (original in my engine) with solid lifters and associated rockers, bushings and pushrods...all Camit. I also installed Camit's thermostatically controlled oil cooler attachment. This replaces the Jabiru one, which has unregulated flow to the oil cooler. The thermostat mod should allow the engine oil to heat to operating temp faster.
The other mods that I have added are all made by Rotec Aerosport (the Aussie company that makes the radial engines). The most significant Rotec mod is the liquid cooled heads mod. If you recall the Voyager (round the world rutan aircraft), it had a one of a kind Continental IOL-200 engine on the rear with specially made liquid cooled heads. The Rotec design is similar to that, inasmuch as the cooling is only in the head itself, not the entire cylinder. The barrels remain air cooled. I have replaced the original Bing carburetor with Rotec's throttle body injector (TBI). That is significantly simpler than the Bing and allows for simpler, more direct mixture control. The overall size of the TBI, also allows me to have essentially a flat firewall. The third mod is to replace the fixed magnet generator/alternator that is integral with the flywheel in the Jab (nominally 17-amps). This is removed entirely and replaced with a more "conventional" belt driven alternator. This Rotec mod comes with a 40-amp automotive alternator. I decided I did not like the integral regulator in the Rotec supplied Chinese alternator, so I bought a B&C alternator of the same size and the B&C regulator to go along with it. I have installed the regulator on the interior side of the firewall to keep it cooler. The overall effect of my mods, once you consider the radiators, hoses, ducting, coolant, brackets, etc. adds about 10 pounds to the overall installation. All up, the engine with everything is about 194 pounds, as opposed to 184 in the original configuration.