Back in 1985 Wolber advertised their Mixte B rim for use with both tubulars and "normal" tires. They claimed it was under international patent and recommended it for 700X23-28 and for Liberty (the Wolber tubular with special repair system) and for cross tubulars. Weight was as much as 520 grams, 32-36h (but Wolber was not the one to err on the light side in weight).
Olof in Uppsala