I use my wide gold colored electric soft mount (http://tinyurl.com/pkufz), the standard size purple plate is shown in the photo but the approach is the same. The A60-24S bolts directly up to it with no modification of any kind needed, it only weighs ~1.5 oz and it is really easy to install.

You absolutely do need to support the back of the electric motors, it doesn't matter whether it's an inrunner or an outrunner, rigid mounted or soft mounted, it isn't a pretty sight when the nose structure starts to let go (don't ask me how I know this). And you won't likely have time to cut the throttle and figure what's going wrong, it happens way too quickly to react to it.

For a rear support bracket I use a piece of laminated G10 fiberglass board material cut to ~3/4" wide that attaches to two support tabs mounted on each side of the interior nose. The cross piece has two slots in it that run span-wise, and the internal supports each have a slot that runs vertically. I use a 6-32 x 1/2" socket head cap screw to tie it all together, with a 6-32 blind nut mounted in a small "donut" of 1/4" thick glass/balsa/glass laminate to act as a combination nut/washer for the screw. The slots allow for easy thrust adjustments simply by loosening the screw and adjusting the crosspiece to mate up to the motor, then tightening the screws back down. It's very similar to the rear support bracket I offer for the C50's (http://tinyurl.com/ntucm), except with a smaller hole in it sized to fit the rear support bearing. I plan on having an anodized aluminum version of it available after the Nats.

As far as engaging the rear of the motor, I've used both a slightly oversized bushing (12mm ID) centered over the output shaft, and also a 10mm flanged bearing with good results.