no need to adjust the metol. i've used an Thorton's A bath with 35gr sod. sulfite per litre and it behaved the same way but much sharper/grainier. i've settled on 75gr for a nice compromise of grain/sharpness. and yes, 75gr is sharper than 100gr. i've tested the difference at 4x prints and have seen the difference. don't hesitate to try it. all the best.