I was thinking you might want a size small frame for your height. I am 6'2" and I just picked up a 18" Vassago 29er frame - it has a super long top tube at over 24.2" long. That is as long if not longer than the top tubes of my LARGE frame 26" bikes.

It might be you are on a frame too big and feel too stretched out on the bike.
What is the top tube length of your current 26" bike? what is the top tube measurement of the 29ers you are looking at?

I usually pick my frames by top tube length. it makes the fit a lot more comfortable for me.

I noticed with the 29er specialized bikes, a rider seem way up high on them. Other bikes it seems the rider is more "in" the bike than "on" the bike.

check out Niner and Salsa - they have a very loyal following and make great 29er frames.