flat 5 is definitely easier than cork 7, no doubt about it. this is how, in my personal opinion you should progress into a flat/rodeo 5.
back flip (definitely be comfortable with these before trying almost anything off axis/upside down.)
flat 3 - very very similar to a backflip, just turn your shoulders slightly and flip back on the axis your shoulders are on.
flat 5 - turn your shoulders a little more (id say roughly about 45 degrees and flip back on the axis of your shoulders, similar to a flat 3 but just a little more around it.) it should come around very naturally.
watch videos of people doing tricks you want to do, play in slomo (if possible) and pause in critical spots to see how they are really throwing it. tramps are also beneficial.