What size bike...

glasgowdan

Dropped it off at a shop for what?

It's a mountain bike - re the comment about shorter stems above, don't listen to it! Shorter stems work very well for technical riding. I'm using a 35mm one just now and it's ideal for me. Longer stems slow down steering and reduce your torque to hold the wheel on line when it tries to flip round against obstacles hit at an angle.

But, no point changing anything if it feels fine as it is.

ab1982

Don’t think anyone can really say for sure its personal preference so go to bike shop to try some. Best advice I had was that its always possible to make a small bike bigger with longer seat tube, stem etc but you can’t make a too bike bike smaller.

Dan83

I'm 5'8 and ride a medium GT on 26 inch wheels.

Unless the frame size's are smaller on 29ers which I doubt, I'd guess medium would be fine.

You could always go to a shop and try one out.

I bought my partner a cannondale trail tango 4 a few weeks ago, she loves it, got 15% discount from Evans cycles.

The cannondale trail tango is the girls version.