[AndyB]

Keep in mind that increasing the number of wheels will no gain your more traction. You'll get the same traction out of a 6wd that you will out of an 8wd. At least theoretically.

You may gain some traction if using wedgetop tread due to it's 'stickiness'. You may also gain traction from using roughtop tread which will actually cling to the carpet. These situations are both relative to a similar setup with less wheels.

The tread you are using looks like standard rubber, unless you are using something else and just didn't model it, which is completely understandable. If you are using this tread, you will likely gain little to no advantage in traction over a 6wd.