MICE: specify record size inline, not in separate header

Merkle Integrity Content Encoding (draft-thomson-http-mice) is a nice idea.
Specifying the record size in a separate "MI" HTTP header feels like a poor design: Content-Encoding indicates the encoding, but its critical parameter is in a separate header.
How about just putting the record size at the start of the content, eg a 4-byte prefix holding the record size in bytes as a big-endian unsigned int?

The 2nd example from the spec would become:

Content-Encoding: mi-sha256
Content-Length: 109

<00 00 00 10>When I grow up, <OElbplJlPK-Rv6JNK6p5_515IaoPoZo-2elWL7OQ60A>I want to be a w<iPMpmgExHPrbEX3_RvwP4d16fWlK4l--p75PUu_KyN0>atermelon

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James Manger