Well, back in the good 'ol days, I only supervised/mentored it being made at 100mg/ml, only cause thats they way someone wanted it, so I don't know about the 200mg/ml strength. Since it's an enanthate ester (methenelone enanthate), i don't see why it couldn't be made effectivly at 200mg/ml though, kinda just like a test enanthate.
it's harder to suspend, I believe the molecules are bigger. It is not like test enth you need to use more concentrated solution to suspend primo otherwise it cristalizes and crushes. There is a way to make it painless at 200mg/ml but not many ppl know how to do it and is not that expensive or anything.