No problem good that the links were of use. Apologies I didn't have time this morning to include the fact that the originally built in the US S22s had galvanised steel keel bolts and nuts / washers which is what you have observed in the links - so totally inappropriate. The Aust built boats (by Gordon Woods a top boat builder) used stainless keel bolts and nuts/washers as far as I know - not sure what grade.
Have saved your photos and zoomed right into the front and rear single fasteners and it sure looks like the washers of those 2 are probably galv steel as per Yara so should never have been fitted. It is not clear however if those 2 fasteners are hex screws or csunk bolts - why are they the only 2 fasteners with filler glue on their top? I would conclude that they are both csunk ss bolts and nuts like the other 4 but the length of the bolts wasn't sufficient for the bolt end to protrude out past the end of the nut as it should have - at least 2 threads out past - so someone has put a bit of glue on top to fill the hole and hide the evidence.........suggest you confirm this next time on board by popping the glue off. It is probably no big deal if they are a bit short - say 1/2 or 1 thread. Please advise?
So when you are on the hard for sure suggest you at least replace those 2 washers and sort out all potential keel to hull sealing issues around the whole perimeter of the keel flange. I had to do this during the slipping of both S22s I owned and it is probable that you will find loose sealant etc. Dig out carefully without damaging the cast iron or keel bolts, seal with 3M5200. Google for the best way to use 5200 and cast iron primer in this process. Be very careful about undoing the ss nuts off the keel bolts to change the 2 washers and also maybe doing the same for the central 4 to inspect the bolts. Stainless fasteners have a very bad thread galling potential see 2nd link below. See 3rd link below for good general article for keel bolt maintenance when slipped. To potentially avoid thread galling spray CorrosionX on the end of the bolt and nut a few times before you slip - hopefully it will penetrate suitably and avoid thread stripping when you undo the nut. Obviously if you thread strip this is dire for a keel bolt but on the slip with csunk flange bolts it is easily recoverable.
www.whitworths.com.au/corrosionx-lubricant-170gwww.anzor.com.au/blog/what-is-stainless-gallingwww.j24.com.au/keel-bolt-maintenance-bulletin/