Weight of A/FX vs B/FX Pontiac Super Duty 421s

[DeuceCoupe]

I am trying to make sense lately of the 1960s NHRA classes.
Have a math question about the 1963 FX class.
Rule book says:
A/FX = Cars lighter than 9.00 lb/CID
B/FX = Cars heavier than 9.00 lb/CID

Looking at the 1963 Pontiacs, all with 421 Super Duty's.
Weights are given as:
PM = Pete McCarthy, Pontiac Muscle Car Performance
DRFS = Larry Davis, Drag Racing the Family Sedan
3300 lb Swiss Cheese Catalina PM pg 153
3300 lb Swiss Cheese Cat DRFS pg65

Now, 3300 / 421 = 7.84 (way less than 9.00) so how did the Swiss Cheese Cats run in B/FX and not A/FX?

A weight of 3790 / 421 = 9.00 seems like the minimum to get into B/FX.

There is a note saying (PM pg156) the Howard Maseles / Packer Pontiac Swiss Cheese Cat ran 117mph in A/FX at the US Nationals in 1963. But, usually, all the Swiss Cheese Cats are said to have run in B/FX.
How could they be this light (7.84 lb/CID) and still be allowed in B/FX ????

DRFS pg66 says the 421 Tempests came in at

3200 / 421 = 7.60 Tempest 421 coupe, ran in A/FX
3450 / 421 = 8.19 Tempest 421 wagon, ran in A/FX
These line up with the NHRA Rule Book cutoff; they are under 9.00 lb/CID so run in A/FX.

The Swiss Cheese Cat does not line up.
Did they ballast the big Cat back up to 3790lb (so 3790/421=9.00) to run in B/FX ? If so then wasn't the Swiss Cheese a waste of time?
What am I missing?
(I was a little young to remember back then)