u are 100% correct on all accounts soonerkid. not bad for an OU fan. :laff: just kidding.not much of a pissing contest when those are the facts, if you want to get really technical class D is individually tailored to the area when instrument procedures exist. so yes, there may be class D that is 5NM (as opposed to SM) but the only time SM is really used with reference to aviation is in weather conditions.
anyway, Class D's are individually tailored and normally contains within it's airspace an instrument procedure. statue miles are only used for visibility. air traffic and pilots utilize nautical miles. don't ask me the difference though. the last 3 towers i worked at that was class D was 7.2nm, 4.3nm, and 5.4nm. none of which is a nice 5nm radius. the 2500agl is USUALLY pretty standard though.