I take no credit for the Knighton - Clyro section. Peter Coulson, when he set up the Cambrian Series rides had spotted how hilly it was between Knighton and Hay, and it features on the 2H, 3C, and 4C (actually Knighton to Brecon). When I needed 10,000m ascent for the 6C to qualify as a Super-Randonee, I simply took the 4C, took the flat bit between Bala and Corwen out and replaced it with a loop into Snowdonia.