brad single and double ex rocker ratios

what is the single and double rib brad exhaust ratio
i thought it was single rib 1.52 and double 1.57
then i see manton has a 1.7 exhaust rocker he calls high ratio
thats a big difference if you figure it on .506 lob lift
1.52 to 1.57= .025 more lift
1.57 to 1.7=.066 more
so what is every body doing
my car ran better with high ratio brad rockers
thanks