Certainly if you want to make 2 at a time, make it at least 4" wide.
My everyday ones are a-boo about 1/4" thick x 4.25" x 37"
The reason I make them 1/4" is if the sled develops a little bow, its flexible enough to let the feed rollers press it down, so the lams don't end up thin or thick in center.
Just what works for me....