Well, considering light armored and armored divisions share the same name, as do motorozed and infantry divisions, in unitnames.csv there shouldn't be a conflict if the H-SUB flotillas start with "1. Unterseebootsflottille" and go up to "100. Unterseebootsflottille". But it's probably a good idea to start with "101. Unterseebootsflottille" and go up to "200. Unterseebootsflottille" to make room for more submarine flotillas.