[Santino]

I'm thinking of adding an 870 express synthetic stock to my collection as my primary HD shotgun.
I own a mossy 500 with a 24 inch rifled barrel and rather than buying new barrels I'm gonna just go ahead and get myself an 18 inch barreled 870, I've always wanted one anyway.
It says on remingtons web site that the overall length is 38 1/2 inches which is pretty short all things considered.
What is the most common length of HD shotguns, anything out there shorter than this not including PG's?, how short is too short ?.....I am 6'1'' 195lbs with average reach.I am not a big time shotgunner and am interested in learning the ropes.I am in no way recoil shy "not trying to be a tough guy thats just the way it is"and I would like to set up my new 870 for maximum HD and god forbid "civil unrest" duties.
What are my options? should I just buy it and leave it stock?
Just so you know I live in a 4 room apt on the 1st floor in nyc