It is hard to say without seeing you ski, but your description made me think that you initiate your turns by pivoting, that you don't use high edge angle (otherwise you would feel the full length of the Yumi) and that you have trouble unloading your skis in the transition between turns so pivoting is hard on the BP88 because it has a longer running length and more pressure at the tip/tail. I think that might be why you prefer lighter skis and shorter running lengths. We all do it to a certain extent, nothing bad in that. I also had that feeling when I bought skis too long for me (impossible to pivot, catching everywhere, and felt too locked into each turn). It also seems to me from your description that you are a beginner/intermediate (learning to carve, starting to ski?, blue/green slopes, etc). However, you seem to be all-in with skiing (2 days per week, taking lessons), so you might be able to progress quite quickly and develop more ski "fitness" (e.g., it usually takes me 10-15 ski days at the beginning of the season to really feel good about my skiing). Still, there is nothing bad about buying the skis that you can enjoy right now and selling them when they feel too short!
When I go
here and put your stats, I get a recommended length of 141-143 cm for a frontside ski (the BP has a wide waist, but it has otherwise the shape of a frontside carver). Can you try demoing shorter skis?
Have you tried the Yumi in soft snow / powder? In these conditions, the rocker is more likely to engage the snow and you will start feeling the full length of the ski...
Hmm, well my instructor has been teaching me short turns by keeping skis parallel to start, letting them fall down the line with gravity, picking up some speed (he calls them starting a J turn) then driving with my inside knee/leg and tipping the pinky toe on that foot to steer. he calls this my "brake" because this is how I will steer my tips uphill to stop. He calls my downhill ski my "brace".
He has been steering me away from putting all my weight on my downhill ski as I am too far forward anyway just kind of naturally. I used to put no weight on my inside ski and it would be all squirrelly in a turn and my knees kind of a-framed so that my turn still resembled a wedge instead of the parallel I was trying to achieve. The wedge and being so far forward made me speed up much faster than I wanted.
To have my inside knee driving, I have to "fortify" it (my own term) and point the knee towards the traverse while pulling the shin of the inside leg under me. Since I was already naturally very forward in stance, I am still forward, but less so this way. I also try to focus on tightening my outside leg at the knee. he calls this gathering energy. At the center of the arc, I start tipping my downhill pinky toe, and that starts a new turn. I "release" the energy when that happens and go back to parallel then start again.
Now I can feel some edge engagement when I do this, though as I said before, far from perfect. I still mess up the mechanics, but that is basically how I try to consciously turn. I found that after I got my new boots earlier this month, the tipping of the little toe (I think I saw
@liquidfeet recommend this too) really naturally started the turn and the ankles kind of follow when I get it right, since my knee is pointing to the side as well.
Of course, this is on a wide open groomed runs with not a lot of traffic at the moment. If there are lots of bumps all bets are absolutely off, lol. I'm pretty sure I do pivot in situations that are not ideal and it happens pretty often on some of the most popular runs whether it's because I am trying to avoid people, or get over a bump, etc. I still skid on steep-to-me steeps.
As for trying the Yumi in a lot of different conditions - we actually had a fair amount of various conditions on my demo day. It had snowed 4 inches the night before and was still snowing on and off so the morning was quite nice. The sun came out at lunch though, so after lunch it had gotten icy in several areas. My husband and I did a blue run called Lucky Shot twice and had to call it by the second time cause it had just too icy with too many people for us to feel in control. We made our way back to the other side of the mountain where the snow was less icy. We also did some bumps, short mogul runs and went into the trees for a bit with my son. I even humored my teen and did "caught some air" on the smallest terrain park bump known to man, lol. I loved how forgiving the yumi had been on my knees so decided what the heck, I'll do a small one. Not bad!
I had a pretty good time in all conditions, but hey, I was in a good mood from how much more in control I felt. Maybe part of it was my mental state? But it seemed to handle much better and my husband, who was doubting me even wanting to demo before, is now a firm believer that I was onto something and I just had to find "my" skis because my technique and form was so much better that day. He is starting to talk about demoing now too, LMAO.