You seem to be a relative newbie hence should've asked yourself a question - maybe you are missing something instead of those "some". It goes as follows: nobody needs early Tony factories - switch R&D to production when it reaches Ki-100-I. Also, you can persevere with small Tojo-IIa production until Tojo-IIc is ready (in late 42 with some investment) and switch R&D to production while at the same time switch IIa factory off. Yes, dormant factory sitting there waiting for the IIb to come at the usual date to complete the upgrade process. While Tojo-IIc will be kicking ass through the whole 43.ORIGINAL: Alpha77
First off, Realistic R&D should be "ON" because "OFF" really gives the IJ too much advantage.
does not matter really
But the discussed feature here, imo not so much... you still need to research (but not build neccessary) most or all interim modells. Otherwise you can NOT switch the factories to produce the next modell in line (I mean the better later one). Those factories will be danmged and need to build up from ZERO again ! Seems some miss this point
In general, switching from R&D to productions is no big deal as long as you reach the useful airframe. Japan has about 90 R&D factories at start, not a loss at all if they are gradually switched to production. You need them producing frames not research points at some point anyway.