Also, to get a 7 deg F rise with a .9 recovery, you have to be doing 195 MPH IAS at 10K feet. Very few RV's cruise at that speed. At 145 IAS at 10K feet, rise is less than 4 deg F (2 deg C).
How did you calculate the ram temperature rise? There is some sort of error in your calculation.
There are two mathematically equivalent ways to calculate ram temperature rise. You can do it using mach number, or using TAS.
Using mach number, we need to work in absolute temperatures.
IOAT = OAT * (1 + 0.2 * K * M^2)
IOAT = indicated outside air temperature, express in degrees K or R
OAT = outside air temperature, in the same units as IOAT
K = recovery factor of the OAT probe
M = mach number.
If you know the calibrated airspeed and the altitude, you can calculate the mach number. In the example you gave, 195 mph IAS at 10,000 ft is M0.308. The standard temperature at 10,000 ft is 23.3 deg F, or 483 deg R. With a recovery factor of 0.9, the IOAT would be:
483 * (1 + 0.2 * 0.9 * 0.308^2) = 491.2
Thus, there was 8.2 deg R (or deg F) ram temperature rise.
The other way to calculate ram temperature rise is to use true airspeed. If we are using deg C and kt, the ram temperature rise =
K * (TAS^2)/7592
In the case above, 195 mph CAS at 10,000 ft is 226 mph TAS, or 196.5 kt. The ram temperature rise in deg C =
0.9 * (196.5^2)/7592 = 4.6 deg C or 8.2 deg F.
At 145 mph IAS at 10,000, with a recovery factor of 0.9, the ram temperature rise would be 2.5 deg C, or 4.6 deg C.
The faster RVs are capable of over 180 kt at 75% power. At 180 kt TAS, with a recovery factor of 0.9, the ram temperature rise would be 3.8 deg C or 6.9 deg F.