Restrap frame bags advice needed

[Tangled Metal]

Anyone own a restrap frame bag?

I'm considering getting one for my London Road bike in the largest size. I've roughly measured inside the frame at the top tube and it's kind of 50cm inside. The trouble is at the head tube end there's.virtually no.head tube showing inside the frame. I think the large version would fit inside the top tube but I'm not sure about the front end fitting inside.

To anyone with one or experience of one please can you let me know if the front of end is kind of pointed out snub nosed/with depth? Am I safer going with medium?

How much stuff does the large and medium take? How practical are frame bags? What do you put in yours on a tour?

Any advice would he gratefully received.