18 too small?

[Zombiechopper]

I'd go 16", you can cut twice as fast because the saw is so easy to handle in bucking cuts especially. This has been my finding anyway.
John

+100

16" on a 70cc saw is beautiful thing

But, hey what do I know. It probably depends on the size of your wood. I love smaller bars though. Much better handling and cuts with so much more authority