HH, too high a fuel consumption, low powered engines?
In 1963, on the NF14 nav trainer we flew with a ventral tank and had a high level cruise time of about 1.30 - a maximum roa of 300 with a combat roa of probably 200.
One aircraft sustained a cracked ventral on a land away at Leuchars. It was recovered on a direct transit but staged through Ackington, MStG, Leckonfield and the final long hop to Stadishall.
Compared with contemporary piston fighters like the Spitfire and an endurance of 2.5 Hours they were very short legged.