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.