File your flight plan using standard airways routeings, at whatever level you want to file.
FL100 is not ideal for that route as mentioned, but that is because of Standing Agreement levels and is of absolutely no concern to you and should not influence your decision... it certainly should not stop an ATCO from granting you entry clearance - just because you file a requested level it doesn't mean you will be given it straightaway or even at all, you may be given a level near to it that suits the traffic situation at the time.
Slow, poor performance aircraft do cause headaches, but they have the same priority as airliners etc. That is why ATCOs get paid the money they do, to sort out the traffic. If your flight plan is unacceptable, it will be binned or amended way before a flight strip gets placed in front of an ATCO.
That part of airspace is very busy - CPT is a magnet and it is not unusual to have aircraft at every available level there, all crossing each other.
Expect to be put on radar vectors, expect to be allocated a level other than your requested one, expect a small delay (traffic dependant there might be no delay) to your joining clearance.
If you get airborne with those expectations, you will not be disappointed and you will have an enjoyable flight.
Last edited by anotherthing; 12th Jul 2010 at 10:15.