I still haven't looked at the ffp solution yet (Loopix' site is not available at the moment) but here are some things I learned so far in trying to manage fps using a lot of models and sprites with overlay on.

1. Sprites aren't an issue as they do not overlap so much as do models like the az_bush available with the A6 downloads.

2. The biggest factor in driving the refresh time for models is skin size. The refresh time for my test bush model reduced by 50% when I reduced the skin size from 512x512 to 256x256.

3. The second biggest factor is scale - the larger the model the higher the refresh rate. But a model with a 256x256 size skin scaled to 2x it's original size still does not put as much demand on refresh times as the same model with a 512x512 skin at the original size.

4. If you skin the 2d branches with a fuller image (ie a branch with lots of leaves and flowers) you can reduce the number of branches required to make the bush or tree look full. This is the 3rd factor - doesn't make a dramatic difference.

Still working on this ... but thought I would share what I have learned (at least for my card and configuration) so far.

Edit:
Between cleaning up some bad blocks, reducing the polygons by redesigning a few things, reducing skin sizes on the bushes, and reducing some branches....
I have recovered my 50 fps. (It had dropped down to below 30 fps for some pov).