I would not take for granted that the ballasts rated for wide range of lamps really can power all of them correctly. Sometimes they are quite borderline for some of the lamps specified, underdriving them etc

I think they would punch the 12w bulbs and under drive the 20w bulbs.

Check their parameters: 12..22W T5 to T12 is really broad range for a single ballast to cover...

Think they weere in the range of .32-.35a

Does not seem right. With 120V mains there is quite a difference in the voltage that would drop on the choke with different lamps, resulting in wider spread of current values for the different lamps

With the currents stated, 350mA is just below the right current for 20W T12 (370mA), 320mA is lower but still okay for the 20W T12, but over the top for a T5....

120v land is a bit of a mess.

The miniature T5 (4..13W), as well as the modern T5HE are 0.17A, the 13W is on the low range, around 0.155A (but needs an autotransformer style ballast - arc voltage is around 90V).

And in that power range, I know no other T5...

What i mean is : All the 4..22 W lamps with quite low arc voltages, that can work on 120V with a choke. Lets say we have 2 of the chokes, both rated for 20W T12 at 350mA. One 120V one 240V

What i claim is, with the 120V one the lamp type will have much bigger effect on the resulting current, because the lamp arc voltage (30..90V) is bigger change compared to 120V then it is compared to 240V. Lets estimate what the current will be with the lamps in the ends of the range (13W T5 or some PL on the high side, 4W T5 on the low side, and for the matter, lets assume 90V can still go on a choke on 120V although i expect trouble), when the ballasts are spot on with the "main" lamp F20T12

120V 30V : 391mA
120V 60V : 350mA
120V 90V : 267mA

240V 30V : 359mA
240V 60V : 350mA
240V 90V : 335mA

calculation done :
I_x = I_F20T12 * sqrt( V_mains^2 − V_x^2 ) / sqrt ( V_mains^2 − V_F20T12^2 )

(substitute the arc voltage of the other lamp for V_x)

(its not accurate as i completely ignore the wire resistance of the coil, in reality the resistance will make the effect bigger for both chokes, and increase the difference in behavior between the 120V and 240V one)

I guess we're having a bit of a math off over here. 

I have the lamps in a 2 lamp desk lamp and they are very bright, but no abnormal aging.  I wished I had bought ALL of them years ago. They were very inexpensive.

I might pick up a few. The ballasts say 12-22 straight tube only. The ironic thing is that I found it in a 13w pl fixture.