The dimorphodon is an agile quadrupedal predator, well adapted for running and climbing, but also capable of limited bursts of flight (similar to the modern example of the wild turkey).  Think of it as a giant carnivorous squirrel.  That happens to also have wings.
(I've had some difficulty tracking down a good dimorphodon weight estimate, but, working off the wild turkey comparison, 15-25lbs seems not an unreasonable number - which puts it as being a roughly bobcat / lynx level predator.)

-1 echoes of the beast (wide-spectrum vision - see deinonychus for details)
-1 claws
-1 wings
-4 supernatural speed (aka: mad scramble)
-2 inhuman toughness
-2 inhuman recovery
+3 catch
-1 snatch & run: use stealth for basic sleight of hand / pickpocketing; unlike the actual pick-pocket stunt, this does not allow complex pickpocketing schemes like acquiring a specific item out of someone's purse or planting an item in a target's pocket - it's more meant to snap up an unattended or loosely held item and then get away - hopefully with the hapless target unaware of where the item went.
-1 bark-brown fur: +2 stealth when in a tree (or +1 on a wooden surface, such as a telephone pole).  Note that this stunt generally will not stack with snatch & run - unless the target item is also in a tree or on a wooden surface.

(unspent: +1)
+6: athletics
+5: alertness, stealth, scholarship
+4: lore, investigation, fists
+3: endurance, conviction, empathy
+2: discipline, deceit, rapport
+1: presence, performance, survival

details on individual forms:
All four forms feature light, white or near-white belly coloration.  Johann generally swaps between them based on which one has the best match to local wood coloration.
male, very dark brown w/ chipmunk-esque stripes, ~15lbs
female, medium brown w/ chipmunk-esque stripes, ~20lbs
male, mixed black-white for an overal grey coloration with only a few hints of brown, similar to grey squirrels, ~20lbs
female, red-brown with black spots - similar to eurasian lynx colors, ~25lbs