OP is 5'-7" & #140 lb, front side skier and like bumps. With the 177 he will just be floating along. The 177 will definitely be more stable than the 169 when he is floating along.
However I believe skis are meant to be driven.
I'm 5'-6", #165, decent skier. I would have no issues skiing the 169 Enforcer as my DD.
IMHO, way too many skiers get longer skis looking for stability. Stability comes from within.
Anyway, stability is not one of the traits I really want from my skis when I'm in the bumps.
If you really want a stable front side ski, go with a cheater GS.
I'm just your size and weight (give or take 5 lbs.), and I found the 169 & the 177 to be different skis entirely. I could ski the 169 just fine, but for me it seemed to have one (short) turn shape in it. The 177, which I bought, is more versatile for me.
I'm not in the OP's weight class, though. I urge him to demo and see for himself.