Unfortunately, putting a small pad on a big machine doesn't get you into tight spots very well.
While small pads will be handy for spot-correction, they won't let the Flex 3401 get into hard to reach areas. The machine's housing becomes the limiting factor. So much so that I haven't bothered using my E2K adaptor nor have I had my buddy turn down my spare backing plate for use with smaller pads. I'll do both of those eventually, but IMO they're not really viable solutions to the tight-spot problem.
Taking off the top handle helps a *little*, but the metal housing (which you then have to hold) gets mighty hot.