incremental redisplay & storage allocation question

[charest@ai-ganymede.JPL.NASA.GOV (Len Charest)]

One of our demo displays is implemented with presentations which may be
updated about
10,000 times during the course of the demo (that is, incremental
redisplay is performed
often enough to cons up a total of 10,000 new presentations). The
display has about 50 
visible presentations, which means that inc-redisplay is generating a
lot of garbage.
The presentations in question are all compound graphical objects (i.e.,
their :printer
uses several graphics:draw-xxx functions).

How can I place allocation of my presentations (i.e., instances of
DW:DISPLAYED-PRESENTATION
or flavors built upon same) under explicit program control? It would be
nice to do something 
like a (DEFRESOURCE MY-PRESENTATIONS ()
	:CONSTRUCTOR (DW::MAKE-DISPLAYED-PRESENTATION ...))
with :initial-copies = 50. But defresource *merely* manages the memory
allocation. How do I then
implement the drawing/printing capabilities of PRESENT? On the other
hand, is there a way 
to instruct PRESENT not to cons a new presentation instance, but rather
to use a supplied instance?

Please respond directly to me at charest@ai-cyclops.jpl.nasa.gov
Our Symbolics mail daemon is on the fritz...

	Thanx,
	Len Charest	JPL AI Lab