Doesn't matter. It's not a bad idea to secure it along bulkheads or other structural members. Strap it in more than two places; straps can break from chafing.

Boats are generally overbuilt and can withstand regular stress pretty well. I once read an article in Wooden Boat about side launching large vessels; they slid a huge ship down a mud bank and into the water on its side. The thinking was: if a boat can't hold up to a little abuse on land then you don't want to stake your life on it in the water. Hey, I would never do it but there's the philosophy anyway

You might want to STORE the boat bottomside up. I've heard of hulls getting dimpled over time - never witnessed it.