There are only 2 ways the capacity can be increased.
Change or modify the crankshaft to increase the stroke, This is highly unlikely.
Change the diameter of the cylinder by boring to a new size. This is probably what has been done.
A common modification to the 125 was to fit a barel and piston from the 200 engine to give 156cc which was relatively easy. I could see that whilst it would be possible to open this up to 175cc I would think that at that size the cylinder would be quite thin especially near the holes where the studs pass through, The cylinder head would also need modification.
Bearing this in mind, I would think the proof would be in the pudding and I would expect to see a worthwhile increase in performance over a 125 model which I always felt needed to be given some "stick" to get it going and made it hard to find grip in the mud.
I'd love to have a try on this beast for myself sometime.
Hope this helps