We report on recent results obtained using an AIX 2400G3HT production-type Planetary Reactor(R) in the 5 x 3 inch configuration for growth of typical group-III nitride layer structures consisting of GaN, InGaN and AlGaN. The optimum reactor geometry has been found by extensive modeling of the reactor design. Increased thermal management allows maximum reactor temperatures above 1400 degreesC. As a consequence of extensive reactor modeling, the process transfer from 6 x 2 to 5 x 3 inch configuration was carried out by simple scaling of the corresponding process parameters of the 6 x 2 inch configuration. The scaling factor is calculated with respect to the changed reactor geometry. We used optical reflectrometry for in-situ growth control during this process development and could confirm the theoretical scaling requirements for obtaining identical growth conditions as compared to the 6 x 2 inch reactor configuration. This is verified by the generation of identical reflectance spectrum features. This important issue of in-situ control is discussed in detail. The TMGa efficiency could be kept at about 17%. Switching to the 8 x 3 inch configuration, the efficiency increases up to about 27%, which is an improvement of 63% as compared to the 6 x 2 inch configuration.