This is what I usually do:
I cut my rubbers to the biggest blade I own (either Clipper, Force Pro Black, or Korbel), basically a blade with head size of 158 x 152 mm.
Then when I transfer the rubbers to another blades (standard blade of 157 x 150 mm), it is a bit overhang on every side (very minimal). It acts as a cushion when the blade knock the table (I hate using side tape because of the glue residue afterwards). And if the rubbers shrink a bit, they fit perfectly fine onto standard blades.
Regarding scissor vs cutter:
I don't understand why I can't cut the rubbers perfectly using scissor, they are always un-tidy. But I do decent job using cutter.
Regarding cybershape:
I talked to a TT store employee quite some time ago and he confessed that it was harder to cut rubbers according to cybershape's shape, compared to the usual round shape. I guess it made sense because for round shape, the cutter can just follow the shape smoothly, while for cybershape, it has drastic turn of cutter passing every corner.
Probably this was the reason that Stiga launched those rubbers?