I'm 6 foot 230 lbs and most 26" wheel bikes fit me OK, but occasionally one will feel rather small. If my toes scrape the back of the tire during a turn, I'll pass on the bike, even if it's a 26er. Some seem a little more compact than others. You just have to get on them and take them for a spin, if they're capable of being ridden at the time.
Generally speaking, bikes with 24" tires are boys bikes. They'll be too small for a 6' 1" guy. I've tried making adjustments to a smaller sized bike like putting on a banana seat, allowing the rider to sit further back, or adding a pair of apehangers angled forward, giving the rider a little extra room to steer, but ultimately it isn't a comfortable ride. Those tricks might work for you on a 26" with a frame that was just a tad too small, but not for a frame that was just way too small to begin with.
Then again, I've always been amazed what some of the guys on here come up with. Maybe you've got the next great idea.