Hodgdon lists the 243 win and Retumbo for a 105gr and 107 gr bullet. The lowest charge is 46 gr and maximum is 49 gr. Also states 49 grains is compressed.
Cartridge Loads - Hodgdon Reloading Data Center - data.hodgdon.com
I just used a drop tube and a fireformed 243 case. Max powder charge right up to the neck is 50 grains.
I'd bet you couldn't get enough powder in the case to have too much pressure with a 90 or 95 grain bullet. I'd use a drop tube and start around 47 gr and work up for most accurate load.