Something Else..
When you step up via the ladder onto a swim platform when the boat is on the trailer, the ladder and the platform absorb your whole weight..
Reason being, the boat does not "give" on the trailer.
In the water, the boat sinks with your weight as you climb up, thereby taking the stress off the ladder.
I didn't think about this for years, climbing up-and-down on my Seafarer's swim ladder, and finally cracked the platform around the ladder attachment.
Think about it...a 200lb. dude climbs up the ladder with boat-on-trailer and it has to support his whole weight without the bouyancy (SP?) of water to ease the strain.
I use other ways to get into my Grady when it's on the trailer.