I don't think it's just the weight of the tower that is the issue, but also the potentially very large man in it. Not to mention any side forces that may be incurred.
The tower I have in mind is around 180lbs and only 1 small man would be up there. It would just be nice for White Marlin, but most likely will not do it unless I can have it tied into the frame. And just a lookout tower no controls. Thanks for your thoughts. By the way how did the boat you saw look with a tower??