My new ewes as shearlings around 90kgs with rams of same age at 130 kgs
For me as a maternal ewe that is 50% too heavy again----but maybe you are aiming to use the Dorper as a terminal sire?
60/65kg seems to be the better weight for a maternal efficient animal here, still gets a 21 kg fat lamb ---need some leeway for an earlier finishing animal of course
Even my Charollais purebreds aren't that heavy
Meat quality will be increasingly important in such an expensive protein as lamb and this may be where Dorper genetics will excel??