So far as I can tell, nobody has installed taller Polini primaries without adding more Thrust through the Malossi 187 cc cylinder, so here goes.
I had bought the Primaries months ago, anticipating the cylinder kit to go with. However my other kidney hasn't grown back so I can't afford the kit until next month. Meanwhile, the SitoPlus finally arrived on the row-boat from Germany - thanks AF1 - so perhaps the modest power boost it is anticipated to provide will allow me to move off the line with my Delta clutch, and lightened weight load in the Polini variator.
In my experience too-tall gears can be compensated with variator adjustment EXCEPT from 0 to 5 as the clutch engages. I am aware that top speed ultimately depends on the engine power to part the wind, and that you can't "gear yourself" up for more speed. But the ET4 153cc does tend to rev pretty high at its current top of 70-ish INDICATED. Perhaps it has a few more MPH in it without the Malossi cylinder. We'll see soon.