Is it a good idea to put CFLs in series?

Having purchased 6 spare bulbs that have a integrated

starter that are 13 watts each, My idea that is percolating

in my head is to put 3  bulbs in series

with each other and drive them with a 40 watt

QHE3x40DL/UNV ISN-SC balllast.  This ballast will

drive 2 or 3 40 watt FT40DL/841/RS/ECO DULUX

bulbs.  In a normal size bathroom two of those tubes are

too much light. The plan would be to place the smallish

13 watt bulbs is a more creative arrangement.  One idea is

to have them spaced around the edges of a 0.5 meter

circular mirrored surface.  Besides, I don't want to spend

the money on the little ballast.

So could someone who knows chime in with an opinion?