10-18 inch wood / 20 inch bar
Upon giving this topic further consideration.
1.) To cut 10-18inch wood it is not required to run a 20 inch bar. The Poulan School of Thought is: " The bigger The Bar the Better it Cuts". This is not True! I have worked with many cutters and most, if not all, used the shortest bar that will get the job done. There are two reasons for this. The first is that the less cutters the less cutters to sharpen and the second is keep as much bar in the wood as possible. Let say you are cutting not 10 - 18 inch tree but actually 8-16 in trees. I say this because most people think things are larger than they acutally measure. With a 20 inch bar in 8-10 inch wood you are cutting with as much as 250 percent more bar than required. This in the minds of many is not safe. The 12 inches of bar not in the wood can easily strike an object on the ground, another log that is a foot from the one your cutting, cause severe kickback and injure the operator
2.) If you really want to run a 20 inch bar for serious wood fiber removal. Then I would suggest an 044 / 046 stihl or an 372xp Husqvarna or any saw in the 70cc class and not something in a 48cc class.