Hi Mark,
I don't have a Mk II but I've attached a picture of the mounting bolts from my Mk1.5. There is definitely a tapped backing plate embedded in the fibreglass. Your boat may be different but a backing plate makes sense from a manufacturing point of view since installing the swim ladder brackets if it was secured with nuts would definitely be a two person job.
The attached picture was taken when I had the rear water tank removed and was renewing the bilge pump hose that discharges at the centreline under the swim ladder on my Mk 1.5.
Good luck with whatever you're doing.
I don't have a Mk II but I've attached a picture of the mounting bolts from my Mk1.5. There is definitely a tapped backing plate embedded in the fibreglass. Your boat may be different but a backing plate makes sense from a manufacturing point of view since installing the swim ladder brackets if it was secured with nuts would definitely be a two person job.
The attached picture was taken when I had the rear water tank removed and was renewing the bilge pump hose that discharges at the centreline under the swim ladder on my Mk 1.5.
Good luck with whatever you're doing.