Since I have access to flying them, I took it up on myself to develop this information in response to this VAF thread on using RV-12's for formation and at formation clinics. While not too many folks are using -12's for that yet, you may begin to see an increased interest in them for formation use. Eventually some, if not most of us, will end up going the LSA route based on aging and medical qualifications so better to be ahead of the curve when approached at clinics
To date, I have about 100 hours in the model and have flown it in a lot of formation with camera aircraft as well as other 'chase' aircraft. It is quite capable and has a max roll rate that approaches what most of short wing RV's (3,4,6,7,8) will do. It does not, however, lend itself to being flown in a mixed formation with those aircraft models. Bottom line, it is quite compatible with it's own kind; other RV-12's in a formation flight. The main differences are cruise speed, weight, and wing loading. With 120 KTS as the max cruise speed it will certainly not keep up with the other models unless they are throttled significantly back. The aircraft wing loading is comparatively light and will move around in the lightest of turbulence. Empty weights are typically around 730-750 lbs depending on additional equipment installed which is about 200-400 lbs lighter than the short wing models.
At this point I don't know any group that has used the RV-12 in a 4-ship formation (although they might already be doing just that). Based on my experience with the aircraft, I think it could be easily flown in this configuration with trained pilots. You have probably seen the young adults flying the Breezers at Sun n Fun and at OSH. They did a great job with a similar aircraft model, so it would stand to reason that the RV-12 can be operated in a similar way.
I have developed some sight reference lines that work pretty well and are easily seen. (See attached Formation Spacing graphics). The primary sight line is the Outboard Flaperon Hinge Bracket superimposed on the Prop Spinner, much the same as the short wing RV's. The secondary sightline is slightly different from what we use now. It's the forward base of the Vertical Stab (specifically the VS-1204 attach screw line) lined up with the Forward Outboard Stabilator Corner (Leading Edge). This gives adequate wingtip clearance and a slightly stepped down configuration. (See Sight Lines graphic). While these pictures aren't exactly in position, you get the idea.
Formation Spacing graphic
RV-12 Sight Line Targets
Formation Model Adam Burch
Position shown slightly acute
Operating speeds should be around the 90-95KTS range which will give outside wingmen some power reserve. Since we have not done a 4-ship flight with them yet, the operating speeds are speculative at this time, but that range seems about right. I'm not sure what max bank angles this will allow until we actually get a flight of 4 in. The Slot, Trail, and Rejoin sight references should be very similar to the short wing RV's also.
So there you have it. Feel free to comment and add additional data as you see fit. I'll try to get further testing in when able so the information can be documented. This info has been forwarded on to Stu McCurdy and a few FFI Check Pilots for their input. The next steps would be to build an RV-12 Formation Syllabus for use in a clinic setting.