With that bar size, you'll be limited to 12-14" dia logs if you want to go through the middle.
However, if you take off the bark slabs to make a cant, then you could tackle larger diameter logs.
I've done 12" ash logs just to slab out 3" thick stock with a 20" bar and it went pretty fast, with a 76cc saw.
A 50cc saw or better will meet your needs if you keep your chain sharp and let the saw dictate the pace.
If you are looking to meet your needs on the spot with materials at hand, then you'd accomplish that pretty well with an alaskan. There are plenty of guys here that have done what you are intending.
If you use hardwood, remember to have a cordless drill along or a brace for pilot and clearance holes for the hardware.
Have fun with this and take a few pictures for us.