Spacers are fine in terms of stability if you have them done properly with the proper length lug bolts. But with the 107s you will need like a 20mm+ spacer to run any of the late model wheels(~ET40 is standard, 107s need ET15-20 if your going for 8" or wider wheels)

20mm spacers are often designed to bolt onto the hub and then have the wheels bolted onto them, this design is use extensively in car racing to assist in changing the track width of the car depending on what track they are racing on at the time. So in my mind they are very safe if used correctly.

Often there is laws against spacers depending on where your from because they become unsafe when doof doof kids install them and dont change the lug length causing it to only be holding to the hub with 2mm of thread(not good) But lucky us, what cop is ever going to inspect a old 107 for wheel spacers