Sounds like a plan, I'd need to stop off for water at various points anyway.
Route is train to Fort William, great glen to fort augustus, corrieyairack pass, laggan, newtonmore, feshiebridge, glenmore lodge, ryvoan bothy, glen brown, tomintoul, south through a glen I can't remember the name of to Gairnsheil Lodge, Ballater, Dinnet, Aboyne, Banchory, Aberdeen to the beech. The latter bit from ballater to the beech is a bit ropey at the moment but I reckon I could get onto the old railway line for the majority of it – I'll be wrecked by then anyway so a flattish route to the beech will be welcome!
Should be cracking four days :o)