Pulling up hills?

["123presto" <123presto@email.msn.com>]

><<  She swears it frees up their back end to push.  What are
> your opinions on this? >>
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Posting the trot seems to be the best way to keep my horse
>from "pulling himself" up the hill and motivated to use his behind
>to propel himself forward.  Real steep hills, I just lean forward,
>grab his mane if I'm freaked, and let him "bound" up them, trying to keep
as
>much
>light contact with the saddle and horse as possible, keeping supple
>with his movements.

This makes me wonder:
I've noticed lately that Zephyr (5yr Arab not gaited) seems to be pulling
himself up hills more than pushing. I think it's just that he is young,
inexperienced and hasn't learned to engage th "other end" yet. I worry about
him overusing his shoulders and that causing a problem (I don't know what
the problem would be :) but it just doesn't seem ideal.)
We ride LOTS of hills walk, trot and canter up, walk down. I ride in an
ORTHO-FLEX that fits him beautifully and he's never had any problems (back
or otherwise). I post up mild/moderate grades, use a half seat on steeper
ones and try to keep my weight balanced over his center or SLIGHTLY back. My
thinking here was that if he had more weight on the hind end he would have
to engage it???

What can anyone suggest to encourage him to get in gear behind? I would
appreciate any advice.
Thanks, Nicole