Hey Skip, you've got all the advice you need about bar length already - 6dl shorter won't make a huge difference, and it's not really worthwhile on a saw that's still got a pretty much new bar. Might be worth it when you wear out the bar you've got.
There are a couple of things I'd try first -
Look into buying a good file guide. I think the only one that is worth having is the stihl fg2, unfortunately they are over $200. They are an awesome tool for teaching the correct way to file, once you've got filing down pat with it your filing in the field with just a file, a file with a simple guide, or roller guide will improve. There are cheaper types that clamp onto the bar, I never had any joy with them, but plenty of others do.
Second i'd try a couple of loops of different chain. Try a loop of full chisel, and try a loop of Carlton semi chisel skip. Both will cut with a little less load on the saw when they are sharp, both get blunt quicker than full comp semi chisel.
The full chisel is a little less forgiving to sharpen than what you have, but much faster when you get it right. The semi chisel skip is just the same to sharpen - but with less cutters.
Personally I find I can usually go a tank without sharpening with full chisel in gum, and if you hit some rotten filth it's blunt in a single cut anyway so I use full chisel more than semi. Plenty of other Aussies use semi chisel or carbide chains exclusively as they are cutting filth all the time. Only you can work out what works for you.
