Hi David, the geometry of the current frame is designed around a 29×3 front, 29×2.3 rear set up, with those tyres you’ll have the geometry that’s on the geo chart on my website. I love this set up because its fast and comfortable, the fat front rubber does a fine job of getting rid of all the high frequency trail vibrations that normally kill your hands on a rigid bike, leaving your arms and legs to act as ruddy great big springs on the bigger stuff. That’s where it should end, but 27×3 front and rear does really nice, lively things to the handling. The gen2 frame was redesigned to accomodate these tyres, but in short, if you’re an ex-bmx type guy who loves flinging his bike around then B+ is the one, and in truth there aren’t any downsides for any type of riding. As you already have 29er wheels why not try a plus tyre on the front, they work fine with regular rims on the front