"Solf Cabin Roof"
I have an O'Day 22..I belive the construction is similar. When you say the glass is broken, do you mean it is cracked open? In that case you can see the core material. If the top of the cabin is "solf & springie" it would indicate the balsa core has rotted because water has got in under the mast step. A possable repair would be to open the area under and somewhat around the mast step (a cutting wheel somewhat like a large Dremel tool works well), remove the rotten balsa & full the area with a solid material such a piece of teak (or for that matter oak). "Bed" the solid material in with something like Marine-Tex. Then use the same Marine-tex to reseat the piece of fiberglass cabin top and the mast step.Next you will need to see that the compression post in the cabin is firmly in place. If not, build it up or replace it with a somewhat longer one. The compression post transfers the weight & downward pressure of the mast all the way down to the keel, it must be strudy! GOOD LUCK!