Can not find parts. Need help or advise.

[Ado Sigal]

>> For the gills I :
>>
>> a.  Took to the liner with a cut-off wheel
>> b.  Cut parallel slots
>> c.   'angled' the plastic between each cut  but twisting while heating 
>> with a heat gun.
>>
>> The end result seems to work well.
> 



Did same type of slots, but instead twisting the slots, I covered them with flap valve material from radiator cowling one way flap valves.


 Also works very well.