[SilverStreak] Black water tank question

[Jotatwcd@xxxxxxx]

My friends have a 77 33' foot SS center bath model.  Does  anyone on this 
list have a model like that and if so, do you have problems with  the shallow 
black water holding tank?  The problem seems to be that there  is only 4-5 inches 
of clearance below the slide valve on the toilet to the  bottom of the tank. 
Even though there is a downard slant on the floor of the  tank toward the 
valve, adding a few gallons of water with the chemical does not  seem to help move 
waste from that area as usual. If anyone has any advice,  please let us know.
 
Thanks
SS owner