Let's see... Taikonaut straps are generally quite thin, thinner than let's say DONs, Europellis, BOBs etc. So you will most definitely be able to squeeze the strap through the deployant buckle. If it wont work, remove the pin (basically a strong spring-bar) on the final piece of the deployant buckle (the piece you see when the watch is on your wrist) and place the strap beneath, then redo the pin back into position. If you have a hard time doing this, simply get the strap wet in that region beforehand. I've done this to several straps and the only ones that did not work were the Cordovans (dense leather).
As for the strap being to long I would not worry about this. The deployant buckle will take about 5mm of the strap, so a 115/75 strap wears somehow like a 110/75 .
Cheers!