I think that any carrier which takes bubs weight on the rump rather than the crotch is ok. With the mei tai, HAB etc. the weight is usually taken from knee-knee along the bottom of bubs thighs/bum and so are fine and don't risk spinal injury.
Also, the Mei Tai and HAB both pull baby in close to you so not all their weight is on their thighs and bottom, a lot of the weight is actually taken from their torso, IYKWIM.
I have a HAB and I just tie it really quite tightly. it is much more comfortable for me and it seems for her also.
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