I'm thinking about modifying an aluminum frame I have...filing a 20mm deep notch into the end of a tube.
The thing that concerns me a little is the tube is closed off at the end. So I'd be effectively cutting off that closure (well not the whole thing, but cutting it in half).
Is there a significant difference in strength between a closed end tube and an open end tube? I suspect not or else seat posts and handlebars would be closed off at the end and they're not.
I weigh almost half of the frame's weight limit.