I can hit flat rails just not the tube ones
Ahh well then ya it really comes down to positioning your upper body and weight to keep yourself up over the rail. You'll also find the slower you are going the harder it is to stay on as you have no momentum pushing you into and glueing you to the rail. That is NOT me recommending blasting in to a rail though, don't risk hurting yourself by going faster than you're comfortable, but committing with a tad more speed may help too. Not sure what board you're riding but I'm sure you know that they can make rails a lot easier or harder depending on the board.