[rcostin2k2]

The top tube seems to have a small removable part, few inches behind the head. Else, there is not much to access the inside because of the seat post and head ... The tension forces favor the model because at that point there is only compression, so the tube closes itself.

[Gravityloss]

Ah, true of course! One indeed can't get to the top tube from the front. But from the rear, I assume you will have to remove the seat but then you do get access to the components deep in the top tube.