Why do I under flip instead of rodeo

I think it means you're dropping the wrong shoulder.

for corks and underflips you drop the same shoulder as the direction you're spinning (left spin, left shoulder) but for rodeos and flatspins it would be the opposite

Underflip you drop the left shoulder, rodeo you drop you right (spinning left)

I find a big difference between rodeo 5's and flat 3's but keep in mind its kinda hard to do a proper rodeo 5 on tramp that will look like the ones on skis because there is no forward momentum from going off a jump. With this being said, I've learned that with rodeo 5's on tramp you really need to think about it as 2 separate steps in the air. 1st is the take off, you really want your whole body to extend up and and to the side, almost like your gonna jump straight up then do a mega hump to something directly 90 degrees beside you, which means dropping the opposite shoulder as the way your spinning to. Its best to practice this step it self quite a few times and jumping up and humping something beside you and up a bit (pretend something #lol) then coming down and landing on your back right at 90 degrees or a little bit past that. once you figured this you have figured out the hardest part to actually doing a rodeo on tramp, step 2 is just the flipping out part which is pretty simple if you have that humping set with your hips down. Once your in the air and physically tell your self "okay I'm done step 1" then kinda tuck up and bit or grab safety (important to always grab after step one otherwise it will turn into a different flip) then almost just back flip out of that so it will kinda be like a backflip 90 coming out of it, its a little harder to explain the step 2 but the main points to remember is think about the rodeo as the 2 different step. 1st set your hips then one you are lying on your back facing 90 degrees away from where you started then you want to kinda flip out of it whatever way you can figure out and you will naturally come out at 5 or maybe 450 the first couple times but you will figure it out boss. Hope this helps man! definitely a weird trick on tramp, wait till you try the 7's or rodeo 9's on tramp lol cuz those get hella fucked

do you mean lincoln loop 180 instead of doing a rodeo 5? to do the rodeo 5 you have to drop your right shoulder when spinning left but drop it more forward. if you drop it down and back it will throw you into a lincoln.

Try to think about grabbing high safety and straighten those legs out. This should open the correct shoulder. On skis front of the binding grabs tend to move our bodies to a rodeo/flat axis whereas grabs behind the binding tend move us into corks/dspin axises