I too have had fuse-blowing difficulties with Cary amps.
With my CAD V12, Dennis Had himself recommended that I replace the 3 amp slo blo with a four amp.
And with my CAD 2A3 SET, Albert at Space-Tech Labs lowered the voltage (and thus the wattage) to a safer level than the excessively high original Had design.
In fact, I am considering having Albert do the same thing with my V12.
It seems that Dennis Had designs his own amps with a very high voltage level for the purpose at hand... it does jack up the wattage rating, but is very bad for tube life, not to mention the inconvenience of blowing fuses of the manufacturer's own recommended rating!