I agree, roof real estate it tight on a class b. For that reason, I recommend you measure and sketch out the available space on your roof.
That way, you'll know where you want to place panels and can get specific measurements of panel sizes that will fit. Then shop many solar panels that are available from many different sources. You'll find some variances in panel sizes and shapes. Some are slightly smaller, some more square, some rectangular. Perhaps one will work best for your space.
Also consider that you may want to run new wiring, but since you can't add too many watts to a class b, you might get by with what you have. Still a good idea to check that.