If you feel that you just don't quite have enough "Power", you can do a little simple clutching.
Pull your secondary apart (Carefully) and tighten the spring by one notch. This will help to hold the clutch back a bit (closed), keeping you in a "lower Gear" longer. It will also backshift a little faster when you slow down.
Primary Clutch (Note: You may want to get a NEW primary spring, yours may be weak from use)
Pull your Primary apart (Even MORE carefully). Your goal here is to make your Primary engage at a higher RPM, and backshift faster. A couple ways to do this is to "shim" the spring, or "lighten" the weights. I preferr the shim method, and I simply take a welding rod (same thickness as spring material), bend it into a circle the same diamiter as the spring, install it in the clutch under the spring. (shim then spring then spring cap).
I have not tried to lighten weights, and that would have to be a "trial and error" method, just make sure that you remove the same amount of marerial from each weight.
I just did the mods to mine last fall (new primary spring, and shim in the primary clutch. I also tightened the secondary spring). Now, it's no problem to spin the Argo around (fully loaded) from a dead stop, on soft ground (lots of traction)