FWIW, it took me about 6 weeks to get past asking this question. Otoh, after riding different trikes over a period of a year, I came to the conclusion (supported by many over at BROL) that "being on a trike" cost me 3-5kph at a minimum despite finally acclimating to it.

(In support of that last statement, read some of brit_sea_power's posts (or something like that) over there about his experience "racing" a Catrike 700. If I remember correctly, he was a young stud, maybe late 20s, who had been a fairly competitive DFer prior to his experiment with the 700. --- Obviously, he was in much better shape than I ever was and came to the same conclusiopn before he went back to DFs.

Sorry if pointing to another board/forum is considered uncouth here, but this is very on point, I think.)