That's actually what I asked in my earlier post. Your intake inlet desgin looks very similar design to the PMAS.
The PMAS filter has a 7" (178mm) opening. Then the bellmouth reduce to the size you want.
I am actually re-design my 136mm 1-piece intake tube with a similar design but is a 1-piece design with everything - no metal part.
Also, can you measure the diameter of those 16 holes in the inlet? I am currently have diameter of 4mm in the CAD now.
I will be unable to assist you...Nick is a friend and his design is patented.