There is a LOT of very different ways to skin a cat on this forum and a thousand opinions...
BUT between Randy Smith and Lee's machine shop----- I have been able to tell those 2 gent exactly what engine I had and what airplane and initial prop I planned to trim/tune with
Each provided me with a relatively low cost solution and further advice...like best muffler or number and size of holes in the tongue muffler
In each case ----now, for 6 different engines, the sale and advice fell in line with the recommendations of venturi size and NVA ( IE total choke area) of Tim, Brett, Mark, and others that pay attention to these details and how they relate to a stunt run on some particular engine
So rather than Roll your own...I highly recommend asking Randy Smith and Lee machine shop and between the two put together a near perfect first time NVA Venturi combo that should work well without too much trial and error
Do NOT forget the great advice to try panty hose/O-ring holder as a restriction--- and keep the intake air clean ----while maybe choking down a too larger venturi------seeing as how the recommend intake filters are no longer for sale anywhere