I'd rather start them off at 100mg or something like that, maybe even lower for the lightest ones. I don't have much experience, but I have seen girls that took too much the first time and it more or less ruined MDMA for them and that's a shame, really. I always think it's best to ease into it, but that's just my personal preference. Some people like to go balls out all the time. Why don't you ask the girls what they want, so they can decide for themselves? They won't know what dosage for what effect, but you can ask them if they'd rather risk going too light than too strong the first time. You can always do a redose after an hour or so if the initial dose is deemed too low. 100mg for a 100lbs girl ought to be quite a good dose anyway. I'm more than twice that, and I felt really good doing 120mg the first times. I'd wait for more people to chime in before deciding, though. Just my two cents 
With my limited experience I've found this to be the best for me as well. I titrated my inital dose up from 70mg up to 150mg, but have to come to realize that I've redosed too much the first couple of times. I'm much more pleased with the effect I get from a good initial dose of 150mg (MDMA powder), and then a redose of 60-70mg an hour and a half after that. If i redose more, I'll feel much worse the following days. If the initial dose isn't high enough, I'm much more likely to chase it with too many redosages rather than just accepting the situation. I'm 6'1, 210lbs (188cm/95kg), by the way.
My girlfriend always wants to do more than me, she's kind of a sensation seeker personality. This means I've sometimes indulged in a second or even maybe third redosing. But really, the last two redosages are not the same as the initial dose and the first redose. I'm much better off lighting a spliff instead. I do indulge with spliffs when on MDMA, and as far as I can tell it's all for the better as reports say that cannabis protects/reduces neurotoxicity from MDMA. For me, there's a huuuge difference between one redosage and two/three redosages. Not worth it, IMHO.
Based on advise in this thread and from Mr.Shulgin himself I think I'll stick to my 150mg initial dose and one redosing of 60-70mg. If I do this no more than 4 times a year while eating healthy and lifting weights 3 x week, I'm quite confident/hopeful that any negative effects of MDMA will be minimal and tolerable. Better safe than sorry.

I recommend taking a 125-150mg dose at once, followed by a 75-100mg redose only if needed. With MDMA, less is more.
With my limited experience I've found this to be the best for me as well. I titrated my inital dose up from 70mg up to 150mg, but have to come to realize that I've redosed too much the first couple of times. I'm much more pleased with the effect I get from a good initial dose of 150mg (MDMA powder), and then a redose of 60-70mg an hour and a half after that. If i redose more, I'll feel much worse the following days. If the initial dose isn't high enough, I'm much more likely to chase it with too many redosages rather than just accepting the situation. I'm 6'1, 210lbs (188cm/95kg), by the way.
My girlfriend always wants to do more than me, she's kind of a sensation seeker personality. This means I've sometimes indulged in a second or even maybe third redosing. But really, the last two redosages are not the same as the initial dose and the first redose. I'm much better off lighting a spliff instead. I do indulge with spliffs when on MDMA, and as far as I can tell it's all for the better as reports say that cannabis protects/reduces neurotoxicity from MDMA. For me, there's a huuuge difference between one redosage and two/three redosages. Not worth it, IMHO.
Based on advise in this thread and from Mr.Shulgin himself I think I'll stick to my 150mg initial dose and one redosing of 60-70mg. If I do this no more than 4 times a year while eating healthy and lifting weights 3 x week, I'm quite confident/hopeful that any negative effects of MDMA will be minimal and tolerable. Better safe than sorry.