I'm not sure.... the bottom of the Hampstead MM won't sag like a Speedy, so I guess it may be reinforced but it's not super stiff either.
When I have all of my stuff inside the MM, there is just a slight "give" to the bottom because everything inside is weighing it down, but it's not saggy. However, I was debating if I should put a piece of cardboard inside the MM like I do for the Speedy. Hope this answers your question.
I'm using the bag like a tote - today I carry all of my stuff plus some folders and a magazine. I really love my Hampstead MM!!