Peter, Hi
I replaced a Houdini on my Jaguar 21 (the type with the bars over the glass). The rubber does perish eventually (thats why I replaced it, it must have been about 15 years old). After I replaced it, it was fine. When I was looking (about 5 years ago), there didn't seem to be a reasonably cheap alternative, and I didn't want any problems in fitting it in the 'hole'. Cann't comment on the 'Grabo'
The actual replacement whent fine, the new hatch was the exactly the same size as the old.
I believe new boats cannot put Houdinis in front of the mast 'due to their using toughened glass rather than plastic', however didn't think this was a significant issue.
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