Deck to hull joint question

[alsail]

Hi everyone. One of the boats I was looking at lately is a Ganley steel hull with cored ply deck and pilot house. I am trying to understand what are the issues with that and if it is worth going ahead.
I understand the advantage would be weight saving , but I am worried about future maintainance problems. Apparently the boat has cross beams and the cored deck sits on top.
A secondary question: The balast is bolt cuts that sit in the keel, submerged in oil. The oil can be inspected and topped up if needed.
This boat is looking very tidy and she is for sale for a good price.
Thank you.

https://www.trademe.co.nz/motors/boa...f61b3b6d56e8f8