In reply to J Brown:
It's a pity, but that first bit out of Perth, as far as the St Madoes turning, is pretty dreadful for any kind of travel except car.
I have cycled it a couple of times, but only because for one reason or another I had to. Both times it was atrocious.
If I'm cycling from Perth to Dundee, I go up to Scone and then to Collace and along the back road that runs along the N flank of the Sidlaws. Or I go along the south side of the Tay, through Abernethy, Newburgh, and Wormit.
But I realise either of those would be pretty challenging runs...