i thought a proper rtc worked in both directions, else it would just be a normal damper.
i've not used one, so i might be wrong!
does it need a prime?
looking at the terrafirma one, it looks like you stick it on, wheels straight so spring is not under pressure and tighten up. if you drive it and it pulls a bit, then undo the spring clamp and move it a bit until it works properly.