I tried a few ways and came up with this workaround - not actually following the curve but the font lets you get away with it...

I made the quad on the left, used envelope to put the text in, duplicated and flipped it to the right, envelope again then added the middle letter in the centre. Broke the letters apart and extended the first and last down.
Not perfect answer by any means but I don't think that Inkscape has the functionality to do this as yet (without manually moving points)
Anyone got any other methods of doing this?