Yea Chad I think you would be fine.  As sean said I don't believe there would be much pressure in the filter anyway.  Depending on the type of cannister the only pressurized area(after pump impeller) would be just a small area and the return hose to the tank.  
As you mentioned they are availiable for heaters.  It's amazing what a compression type fitting and or an oring will hold as far as pressure is concerned.  I remember seeing a probe holder once that goes onto your return plumbing on your tank.  Another item that's along the same idea.
I'm excited to see this mystery project! 

 
		
	
		
		
		
		
			
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				No matter what the morrow brings, inventors keep inventing things.
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Jonathan
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