I used 200lbs for 2 sets of 5 the last time I did them, using an olympic grip, pretty close to failure on the 2nd set but I'm weak
Although I did do several sets of power cleans, full back squats before hand.
Use a wider stance to help you stay more upright. You can also use wrist straps around the bar to hold on instead.
Its normal to feel like your drowning in them.
They transfer much better to vertical jumping power in my opinion.
I saw a 180-190lb Olympic lifter front squat 800+lbs with a slow controlled negative.....