For the most part, all of the 300 + RV-12's now flying are built pretty close to the same, and they are flying with the exact same propeller blades / propeller, and engine.
With this being the case, and because of all of the data that has been acquired during extensive flight testing, using static RPM as a cross check has proven to be a very reliable way of setting propeller pitch.
All of the S-LSA RV-12's produced so far (~ 25) have had the prop pitch set to a specific pitch value (established by testing), and then cross checked using static RPM. They all perform nearly identical.
Density altitude condition at the time the static RPM check is done has some effect, but to a large degree it automatically compensates.
I.E., someone flying from a higher elevation airport (say 5000 ft) will be adjusting pitch to a slightly lower value to attain the proper static RPM, because of power loss with the higher altitude. This will automatically dial them in to a pitch that is better for the environment they are flying in. If someone is flying in a wide variety of density altitude conditions, they will probably want to adjust towards a slightly higher static RPM than nominal, if the are doing their checks and adjustments at a low density altitude.
A static RPM of only 4800 is not a best all around performance setting for an RV-12. In fact it is likely that the airplane is not any longer legal as an LSA because it will be able to easily exceed 120 Kts at zero density altitude and max continuous power (as already hinted at in a previous post made by the O.P. in this thread ). Also, at higher weights and density altitudes, it's takeoff and climb performance will be noticeably worse than most RV-12's
On an RV-12, a full throttle static RPM of about 4950, does provide a good all around performance pitch setting. The check needs to be done with no wind, the oil fully warmed to normal operating temp, and the density altitude on the ground, somewhere in the ball park similar to the conditions being flown in most often. If this process is used, doing the check at different times of the year will automatically compensate for major temp swings with the seasons (such as people in the mid west flying in the winter with temps in the teens and 20's, but in the 90's or higher in the summer).
After some experience, most owners learn a preferred pitch value for summer and winter, and then just switch back and forth between them. Here in the pacific north west, we don't have nearly that big of temp (density altitude swings so we pretty much use the same pitch all year round).