I need to replace the carpeted bunks for my trailer - holds a 17 foot
aluminum bass boat.

Have thought of a few design changes and wonder if anyone else has
done similar or if they may not work well or be worth it:

Replacing the 2x4 with a 2x6 for better boat support? (boat sits on
the wide side). I also wonder if it would be easier to winch the boat
up on the trailer due to more surface area for support?

Using through bolts (carriage bolts with stop nuts?) instead of the
lag screws?

And has anyone considered using the composite lumber you can buy for
decks? I'm thinking you wouldn't even need to carpet it and the boat
would slide on and off very easy - maybe too easy? And of course it
would last forever.

Thanks in advance for your suggestions.