I used to dose LSD with harmalas quite often. Dosage wise, 2-3.5 grams of syrian rue worked nicely, but I actually preferred using 500 mg of a 50:1 caapi extract (unusual for me, for most tryptamines I prefer using syrian rue). Generally this was with 2 hits of LSD, ~80 micrograms per hit if you put faith in knowing the dose of LSD.
Harmalas do not potentiate the LSD trip as much as with DMT or mushrooms, but I noticed enhanced visuals (literally, swimming through curtains of them). The trip lasts longer too - up to 20 hours rather than just 12, which can be kind of annoying when you just want to go to sleep. Generally LSD + harmalas was a pleasant combination, the only time it went sideways was when we did 3 hits of LSD with caapi extract, then also smoked joints sprinkled with 5-MeO-DMT while coming up. That turned into a 24+ hour very weird trip, we couldn't speak for hours and one of our tripping companions passed out for a couple seconds late in the trip, after having a puff of hash. It took her a sound sleep and a good meal the next day with meat and red wine before she felt grounded again.
I'd make sure the identity of your LSD is confirmed (you probably want to try it on its own too, to get a feeling for the batch) before combining with harmalas. I have no idea how a DO-x or some of these NBOMe-thingies would combine, but it could be dangerous.