In the battle to obtain the higher volume and deepest vacuum as the holly grail, I discovered that there are solutions that do the job in a very interesting way:
https://www.idealvac.com/Roots-Blowe...umps/ct/1362-9 (no affiliation with them)

the idea is there that a high volume pump is connected in series with a pump that is doing a much deeper vacuum, resulting in a new pump with almost astonishing results: +1000M3/h and 99% vacuum with 8kw!. The trouble there is that such a pomp costs in the range of ....30k+usd

So I was thinking why not trying a combination of the a side channel blower (single stage) with a vane or any other dry pump solution.
After reading for a while about them, it seem that the principle is worth a try in the real world (most probably others tried it also).
The advantages could be great:
- high volume deep vacuum
- single stage side blower and low volume vane pumps are available in the second hand market at reasonable prices

my main 2 concerns are:
- side blower delivers a too warm air, and the second stage pump needs a better cooling (a ring pump as second stage can maybe handle this)
- side blower does not provide a deep enough vacuum for the second stage to be able to process it for higher speed

So my question is now: anyone suggestions on how to proceed?
I have a blower and a claw pump that might go into such a trial . Plus a couple of inverters if needed.