I recently asked on the Facebook, GF9 Tanks: Modern fan page, if anyone plays of a larger than 3' x 3' table in a variant.

Scott Savory used a 4' x 6' tabletop, at a 150 points per side...

Name:  50466392_1743741422396893_5823087802031538176_o.jpg
Views: 81
Size:  98.3 KB

...the building are from Battlefront's "Battlefield in a Box"

Other sizes mentioner were: 4' x 6'; 4' x 8'; and 3' x 6'.

4' x 4' was a very popular size, with 200 point armies, such as Ian Gardener's....

Name:  50230743_10156002804005868_8913823929831784448_o.jpg
Views: 68
Size:  89.6 KB

I'll be looking to try these sizes out!