Just bought a 2019 Mmmbop frame off ebay for super cheap. Hoping to transfer components across from my 29er FS to test it out first. I've read someone on YouTube has got a 29 x 2.3 to fit in the rear. Has anyone tried converting it to 29 and would a low tread 2.4 fit?
Remember to shave your legs for improved aero too.
Seriously though, wheels and tyres are the best place to start, particularly tyres. A faster rolling tyre can often make more difference than saving a load of weight.