Boat lift bunk board question

Thanks for the feedback Pete. This gives me some confidence. I was most worried about the shear strength of the bolts holding the board to the bracket.

For the engineers: I bought a used hydrohoist without bunks (they were stolen). The brackets for the bunks are there which are 2x2 angle sticking straight up. I plan to attach 2x material to the angle with bolts similar to many cable hoist setups I have seen (plan to round edges and carpet). It is a 4400lb lift and the distance (length) between the angle brackets is ~12’.
-what size board should I use?
-the board will only be held by the bolts unless I weld on a tab. Are bolts sufficient and then are two bolts per bracket sufficient?
-plan is grade 5 galvanized bolts. Should I consider others?
Appreciate the feedback.