More words of wisdom from C4′s D. Parmenter (and another trick question, too):

What’s the Best SUB On Which To Learn — A Long Single-fin r a wide quad-fin or a short tri-fin, etc?
      Actually, the best board on which to learn is a borrowed board. By all means, learn on the biggest board you can find, but before committing to a purchase go out and demo everything you can get your hands on.
       If you can master the basics before you buy your own board, you will be more likely to end up with an SUB size and shape that won‘t hold you back when you begin to progress.
        Purchase an SUB with an eye on where your skill level will be two or three months from now——–not for the first few days when you are wobbling over the waters of your local inlet or lake.
       After all, there’s nothing worse than finally learning to crank a snapback while leaning on your blade, only to realize to do so on your 12’-plus leviathan will require a truss and two tugboats.

Stand Up Paddle Surfing Equipment by C4 Waterman | SUP Read Me | Paddle, Board,       , Standup, Sub