Am also interested in an off-road route from Inverdruie to Nethy Bridge.

ta

You can do a nice loop using the Slugan and Ryvoan passes. It's not exactly technical but it's lovely riding. There's a cycle path all the way from Inverdruie to Glen More now too.

Hunners an hunners. Get a map and pick a route. Even the crap ones are good.

Inverdruie – tracks in Rothiemurchus to Glenmore – Ryvoan Bothy – Eag Mhor gap to Dorback – road bimble to Nethybridge.

I'd second the Eag Mhor gap. Some great riding in there.

some nice trails off the forest track between Badaguish and sluggan

Too much nice singletrack in the forests to name it all, although we did walk around loch garten and loch mallachie and there was some great rooty stuff around there which then linked you back to the speyside way.