Re: Acoustic Body Shapes...
Seagull's are a great choice, as for shape, IMHO it generally goes like this:
Dreadnought - strumming, flat picking, will handle more aggresive strums.(only beat by a jumbo in loudness.) - also can be finger picked and is by many.
Jumbo - great for strumming, loud voice. Can be used for other things but strumming is its strength.
Parlor - can be strummed but not to aggresivelly, great for blues leads, good finger picker, great portability.
OM - ochestral model - finger picking speciality, quiter than a dreadnought, can be strummed, but not really hard, it will lose its focus and get muddled.
In your case I would consider a dreadnought, maybe with a cutaway to help with upper fret access, but the cutaway may cause some small loss in bass response.
But as stated by someone else, try one and see what feels and sounds good to you.
Hope it helps