DS definitely wasn't putting weight on his legs at 8 months. He did like you described and would curl his legs up if you tried to encourage him or get him to bounce (even now he still curls his legs up if I try and get him to stand or bounce). Our MCHN wasn't concerned though so we weren't referred. Probably because he was commando crawling and was using his legs kicking etc. He probably started putting weight on his legs at around 11 months and then pulling himself to standing at 12 months. Now, at 13 months he is cruising the furniture.
I wouldn't be too concerned at this stage since babies vary so much in their development.