it makes em so much more comftorable. I did it three times, finally the last time i was pretty stoked with the results, except the innevitable heat from the video receiver, only reason i gave em up. The first try i tried just cutting a slit in the lens like the others you see available but the screens wound up too far from my eyes, started loosing the perfrial vision they had, yada, yada. i tried a set of normal sized goggles and tried putting everything inside the lens, it all wound up too tight, the plastic frame was back to pushing on my face, etc. The third try i went with a ski goggle made for wearing with glasses. There deeper than normal and imo have better venting. All i did was use black spray paint over scotchbrited lens on the inside. put the lens back in and got all the pieces in there and had to do some shuffling to get the monitors as centered as possible without beating up the rest of the parts. I ran into one problem where fatshark sent me a part to fix video tearing and they had to come apart. By the time i got the glue and crap off, i had broken the antenna input on the board, pcb cracked in half, but luckily was the rx part you buy seperate for fatsharks and was $30
this is what worked for me
see how the monitor is offset, never noticed wearing them, but that's the whole trick, getting them big enough to make not noticeable
there is also this guy selling them, might look through for more refined ideas
http://www.fpv-plastics.com/FPV-Plastics/Welcome.html