I cannot see why they cannot be used with any fibre cartridges. Overbored? Have two GTi's which are 18.8 and shoot fibres without any problems whatsoever.
All this fibre wads are no good in over bored barrels is the biggest load of tripe going. Shot loads of fibres through over bored 525's, 725 and DT11, never had a problem with any of them, clay and game loads.