This is exactly the same situation I am in, sproggle is 7.5 months.
Although I have used my Close Carrier a lot, I did find it was too big for me, the 'cross' at the back would rise up to high - even with someone holding it down when baby was put in the 2 metal rings where too far forward. Not too mention all the excess material. Were as it fitted my husband perfectly.
Due to finding the 'the one size fits all' of the Close, doesn't actually fit everyone, I did some research & narrowed my choice down to Ergo and Rose & Rebellion. I had very short, unhelpful customer service reply from Ergo and lovely, very helpful customer service response from R&R, so I ordered one. It arrived yesterday, it looks stunning.
You get a 14 day home trial, can't be worn outside. So I'm testing it. I had it on for over an hour yesterday doing Wii Fit Plus - I reckon that'll mimic long walks, with stepping up & down & stuff. Yesterday I did basic step, advanced, 2 lots of hula, skateboarding, obstacle course, ten thing, kung fu & cycling - baby fell asleep during this . During the exercise the carrier felt fine & I had no problems or pain, sproggle really enjoyed it, getting her to nap isn't easy.
My back did feel a little achy around where the waist band sits for a little afterwards, but it was the first time I'd worn it & for quite a while being fairly energetic. That wore off an hour or so later.
Will do more testing & report back.
I also fancy a woven wrap as back up.