I wrote "White Velvet" this morning.
All of the instruments are GPO. I made extensive use of the violas in their lower range. Don't overlook the viola section in your own works. Their low notes can add a chordal lushness and sonority. Double-stopped or divisi violas combined with celli that are playing the root of the chord, can be very effective. It's a very full sound and involves only two sections of the orchestra.
My best to all,