I've always felt the working memory, and also just recall in general, was my limiting factor in doing certain kinds of math (not for lack of interest or trying). In cases where the problem is solved by understanding some underlying structure there is no particular disadvantage... but the rule-execution, manipulation of equations, substitutions, etc especially when done in the absence of conceptual understanding is really challenging.

I've got a similar cognitive profile to what you describe - ceiling verbal, above-average everything else, barely average short term memory which is probably only average thanks to compensation, with a history of so called "careless" in math - and this is an area where I want more ability, so I'm eager to see the next post.