[ODE] Stacking objects

[Jeffrey Smith]

I've been having serious problems with stacking objects stably in ODE.
This has led me to investigate ODE's stepping and LCP solution 
routines, where I've noticed that you can track the error of the 
constraint satisfaction in dInternalStepIsland_x1 (at line 566).

I've noticed that during normal, "happy" steps this error is between
10^-3 and 10^-1.  When stacking objects, however, this error shoots 
up to 10^2 to 10^4.  Clearly, a bad thing.

How can I reduce this error?  Is there any way to do the step "more
carefully" (presumably with a higher cost) if I detect that the error
is climbing?  Would fixing ODE to use doubles instead of floats for
dReals affect this?  Is there a more robust LCP solution technique
that I could implement to fix this?

Any experience, ideas or suggestions would be appreciated.

-jeff