Making my first four and five tier wedding cakes this spring.  I usually just use bubble tea straws for support, but are they strong enough for the bottom (12 inch) tier?

Have you looked at SPS?  Best support system, IMO.  Cheap, sturdy, easy.

Do you know how hard it is to trim the pillars?

I have used straws for 4 tier cakes but SPS is probably a better option.....they will be reusable :)

The idea is to make the height of the cake tier match the pre-cut pillars.  The pillars come 4", 5", 7" and 9".  To cut them you need a hack saw or chop saw.  (But that's also why its so sturdy.)

Thanks for your input!