FTIR object multitouch

hello people, im trying to build my first multitouch display for a project in university based on frustated total internal reflection, and i found some doubts on the way and i hope that somebody can answer,
first is a question about the stup of the table, until now i have the acrylic and some leds powered, i can see my finger blob not so much, but the problem cames when i put an object as a cup for example, i dont see anything, i hear about to put a silicone rubber sheet over the acrylic to intensify the ftir effect, anyone has experience with this? it will work with a cup? , how can i get it?
the other question is about the contour module,about the out pin y position, its a little buggy for me because it dont keep the ids of the finger/object when i cross to objects, anyone experience his? thanks for such a great software that let us make this kind of crazy stuff.

your first question better put here: http://nuigroup.com/forums/

and regarding the second one:

it dont keep the ids of the finger/object when i cross to objects,

what do you mean therewith?

take also a look here:

http://tinker.it/now/2007/02/28/multitouch-table-experiment/