I thought my palpating was good until I got an ultrasound. Easy to palpate for me at 20mm or more. I use the ultrasound to see which girls to start breeding. I don't put a male in until the follicles are 10-15 mm.
Hard to palpate those with 10mm vs 6mm.
So at this point I only have 2 girls at 12 and 15mm follicles so I am only putting males in with them at this point.
Seems to allow me to use the boys more efficiently.