Thanks Bud/Darren!
Darren - no the frame is NOT built in. It just appears that way in photo - frame is separate unit (plastic).
On a side note
What would you think about placing a piece of aramid (nomex) material such as is found in fire proof clothing, on the underside of the foam element (between the foam and the plastic skeleton a/c frame). If the carb back-fires, the aramid material would prevent the fire from reaching foam and perhaps from melting it?
Aramid material (military uses it in flight suits) is good for flash-fire protection (i.e. short duration) up to a certain temp (can't recall max temp.) and does not melt.