You can see a semi-overview of layouts here
https://dl.dropboxusercontent.com/u/31543901/AgileVisualization/Layout/0107-Layout.htmlor inside image in Roassal Examples > Layouts
It may be my imagination, but I think Natalia Tymchuk was working on a faster version?
In any case, you can specify number of iterations for ForceBasedLayout with nbIterations:
~~~~~~~~~~~~~
RTForceBasedLayout new
nbIterations: 1000;
on: elements.
~~~~~~~~~~~~~
obviously with fewer iterations the layout will get worse.
Also, how many elements is "many"?
Peter