snip

The *total* max load should be marked on it somewhere. Because it is
externally the same as another doesn't mean much. So if it says 20w that
is the maximum.

Hmm, the only rating in watts on the transformer is 20w. I just find it
hard to imagine that a 5 way transformer would be rated so poorly, I
mean do 4w bulbs even exist???

Cheers