Either will work fine, just depends what you want to do with it. I've run tanks in series (main tank, header tank) and in parallel (twin 11 oz. saddle tanks in a DF model).

Of course, both have been set up for glow with muffler pressure. The header/master tank's most obvious advantage is the constant pressure the carburator "sees". Even with the twin saddle tanks, the fuel is drawn suprisingly even from both tanks.

If it's gas (with a pump carb), either should probably work okay, though I would tend to lean towards the header/master set up. If you're flying so long that you run the danger of running one tank (saddle set-up) dry, either fly shorter flights or go with the header/master set up.

Sorry for the either/or answer, but I've used both with equal success.
Daren