I currently ride a 29er with a 24.3 inch top tube, 90mm stem and layback Thompson post.
I've just ordered a SC Highball frame with a 25 inch top tube; while I know ladies would say 0.7 inches can make a huge difference, would most of you just get shorter stem and have done with it or am I going to notice a massive change in handling because the frame is a little longer?
Thanks
Difficult to say until it arrives and you've got it built up how it will handle in comparison.
Though I'd do exactly what you've said, and lose the extra length off the stem to compensate. I don't think it will matter that much, handling deficiencies usually creep in when fitting an overly long or short stem to compensate for a bike way too small or too big, a 15mm shorter stem will be well within the realms of normality.
The other option is a large frame (rather than XL) with a 24 inch top tube but the head tube is alot shorter and I don't fancy a ton of spacers.
Your certainly going have plenty of choices in getting the bike right for you! Layback, you could go straight, saddle will probably come forward a little or, as already said, the stem can give you that 10mm to 15mm back. I wouldn't worry too much about it as you'll love it either way! Stick with the parts you have and see how you go.
Good luck.
I don't know whether the TT length alone will change the handling significantly (no doubt someone will claim to) but presumably there are other differences and so it's bound to ride differently anyway. I'd wait till you ride it before mucking about.
Kind of the basis of modern MTB geometry really - longer top tubes, allowing shorter stems and faster steering.
If you're currently running a 90mm stem and a layback seatpost on a bike with an eTT of 24.3", it doesn't sound like the large with an eTT of less would be a good idea. Personally I'd get the XL then experiment...if it handles alright with a 90mm stem, I'd go for an inline seatpost.
What frame you got currently?
I'd look at the geometry as a whole, not just TT length. If your current bike has a steep seat angle, that might feel like a longer TT but with a more relaxed seat angle etc.
Currently got got a 2008 Kona Unit 2-9, 73 degree headtube angle and 74 degree seat seat tube versus 70 degrees and 71 degrees on the Highball; Now I see that written down it makes sense why the Kona handles so badly in the singletrack
Looks like 70 and 73 on the Highball, at least if you look at the Santa Cruz website...
[url] http://www.santacruzbicycles.com/highball/#geo.php [/url]
With a slacker seat tube, I'd go longer TT and inline post, maybe lose 10mm off the stem but no more. And yes, that is a steep head angle on your Kona, my old 29er Inbred felt a bit sharp with a quoted 72 degree head angle when I had 80mm forks on it, it felt sooooo much better when I lengthened them to 100mm.