So I decreased the height of my cage and got the 260W panel heater ( viewtopic.php?f=95&t=21958 ), which is now mounted against the roof of the warm side (it takes up a little less than a third of the cage's length). I have also put in a screen and a thermostat.
My cage setup is now as follows:
2.00m (L) x 0.6m (H) x 0.6m (W)
Warm side: 2 x 20W heat pads + 260W panel heater on roof
Warm side temp: 29*C (runs at 32*C without thermostat)
Cool side: No pads etc
Cool side temp: 19*C
Is the 19*C on the cool side still too low. Will the boa not move across to the warm side if he needs heat?