Replying to Having trouble with backseating 3's

Well, maybe backseating is the wrong term. About 3/4 of the time I throw a 3, I can get the rotation fine and land with my feet straight at a normal distance apart, but I'm like almost laying down from having my weight waaaaay too far back by the time I land. One thing my friend noticed is when I throw my arms around from pre-winding, I throw them to the left, and a bit up, could that be throwing me off balance? If I throw them straight across, my tips go down and I can only get like some sort of nasty flailing 270. The other thing I thought could be a problem is the length of my skis. I know it isn't all about the equipment, but I have tiny skis right now, 153cm invader minis from last year. (I've grown a lot since I got them) I'm about 5' 6 now, and I'm about to get 171cm invaders, since my 153cm minis just broke. Will the longer ski help my balance, or just slow my spinning? Any help would be great, I just can't seem to land quite right. Thanks.