Giant Roam 1 W Upgrade Help
I recently got my gf into riding with me. Picked her up a 2011 Giant Roam 1 W a few months ago. Well, to make a long story short she's graduated from strictly commuting to riding the dirt trails. She's having trouble keeping up with me on the singletracks. I know it would probably cost less to get a new bike but it took us months to find a frame that fit her right and allowed her to stand over the TT comfortably (she's 4'11"). Based on her observations she seems feels more comfortable my 29er because of how light it is (22lbs) and how much more stable it feels in the dirt. Now the frame wont allow 29er tires so I'm thinking about a 26er setup. Here's where I need help.
1) I'd like to replace the fork. Stock is a Suntour 63mm fork. Would a 26er fork with 80mm travel be ok on the bike? Or would I need one with more travel to compensate for the smaller wheel? I don't want to change the geometry too much.
2) I have a Shimano XT groupset I'd like to migrate over to save her some weight. Everything would fit fine except for the BB. The Roam has an internal BB while the XT has an external BB. Stock, the Roam comes with the Acera cranks. What's an upgrade to this that will work with the stock BB? Or, is there any way I can get an external BB to fit the Roam?
Any help would be appreciated. Thanks!