I think that out of combat, I would be pretty liberal in granting a circumstance bonus to Stealth for using a floating disk while invisible. Certainly it would negate most terrain-based penalties. I wouldn't have it turn you into an undetectable stealth drone. Against alert opponents the bonus would be lower. In combat I wouldn't give any bonus. (I'm unsure in general about the use of floating disk in combat.)
I'd also be willing to try a house rule allowing use of Arcana instead of stealth, though I wouldn't give any special bonus to that check. I'd allow enemies to use Arcana instead of Perception if you choose Arcana for your check.