Surfing Waves

Hi,
I am living in Peru (Huanchaco) and pretty much all the waves go left.
I'm 5ft 8 and have been learning on a 7.0 funboard (a bit slimmer and pointier than a minimal).
I have been frustratingly persevering with the 7foot board but never really making it down the line or into the beach because of falling off the back somewhere on the face of the wave or running out of steam on a flatter section of the wave.
The last couple of days I've gone back to basics with a 9ft longboard and am riding into the beach on small waves, no problem. However on steeper waves I'm still coming off the back of the board.
Since the longboard is slower I'm getting an idea of some of my mistakes, dragging knee on takeoff for example.

Do you recommend sticking to the longboard until I've corrected all the errors or alternating with my smaller board?
Any general tips for riding backside?

Thanks a lot!

i'd say stick with the longboard at the moment, and perfect your technique, e.g dragging your knee and so on. By doing that when you do downsize to a shorter board you'll have a much better technique perfected!