Looks pretty cool.
I did a M1A1
this summer, so I know all about trial and error
. I used a pretty detailed ref pic and a tamiya model as reference. What kind of reference are you using?
As for the model, are you going for high-poly or more medium/low-poly? If you are going for high-poly, I'd do as RickStefani said and bevel/chamfer those edges. Byrons Bevel on highend3d is a very nice replacement for mayas bevel. I also agree on staying away from booleans as much as possible, as they can result in some very 'unclean' geometry. I did the main shape of the vehicle first and added details later, but that is mostly a matter of preference.
Keep it up and continue using PLE for as long as you need to. The watermark is ugly and large, but does not totally obscure the model.