Funny, because before reading your last answer, I tried 2000, which didn't really improved, so I tried 10000 with the following result:
Massive hit on frame-rate, which dropped down to 33 FPS and generated anomalies. First, I simply didn't had the smoke rendering, only the flams, which were, I admit, much better and these ridiculous amazingly unrealistic slag flow.Then, after maybe 1 second, came the smoke in a ridiculous very strewn rendering in an "Indian smoke message" mode !!! Simply HOR-RI-BLE, believe me ! LOL !
Also something I didn't mentioned until now, which always happen (in all tests and configs):
When the booster are ejected, the plumes remain attached to the booster and therefore, you can see these plumes making a gracious circular arabesque, according to the booster rotation, before they disappear ! This is horrible too !
Sorry to say that, but for me, these solid rocket plume flames are just a catastrophe right now ! Almost speaking of the RT-10 "Hammer", but also the Ariane 5, I tested yesterday seemed bad, and probably most of all other's. OK, my PC is probably not the most powerful one, but 16GB RAM with an Intel 7700 PCU and a 1080 GTX GPU, should be able to run this.
I don't know how you obtained the plumes you showed to me on the pictures in your first answer, but I really doubt this is feasible with this mod on an actual KSP 1.10 installation, on a PC like mine.
Hope this feedback may help to improve in the future and me, for now, in the meantime, I will remove all these flames, to obtain vanilla version instead.
Cheers Zorg !