I have the Camvac 336 with twin motors and 2.5 inch inlets which I brought back in the day when Camvac was still owned by the family which invented them so it is a good few years old.
I am probably tempting fate here but I have had no problems with it at all. One tip I was given is to run the pipe work in the same size tube as the intlet and only alter the size at the last moment this is to get the most suction from it, also if possible avoid 90 degree bends as far as possible.
My workshop is my garage and I have the piping running along both sides of it with blast gates at several points and at each outlet. It currently serves 2 lathes and one spare inlet on one side and the bandsaw and a spare inlet on the other and is about 9 to 10 meters in total length. I have a friend who installs vac and air conditioning systems and we did a test to check on air flow and according to his equipment the loss of suction was negligible at each outlet.
Over the years I have made a couple of changes to it to make it better the first one is to reduce the noise and heat output in the shop. I have a false wall across the front of the shop to block the double doors and there is about a 10 inch gap between the wall and the doors. I have put a hose on each of the motor outlets and piped it through the wall this reduces the noise considerably and also keeps a lot of the heat out of the shop. If it is very cold in winter I can pull the hoses back into the shop for extra heating if needed, there is still a fair bit of noise but this is coming from the air inlets and there isnt anything you can do about that.
The other problem with them is cleaning them out I found I was having to do this at least once a week and sometimes more due to lose of suction as well as the bin filling up. This involved taking the cloth bag out and cleaning it and then emptying the collection bin, I have a couple of spare cloth bags so I used to wash the dirty one which was not the best thing for the washing machine or the bag. So I brought some disposable bags for it these ones
https://www.equip4work.co.uk/cleaning-and-hygiene/vacuum-cleaners/accessories-and-spares/numatic-10x-nvm-5bh-hepa-flo-open-filter-bags-604020.html and that made life a lot easier as once they get too blocked you just throw them away and put a new one in.
It still didn’t solve the problem of having to take the camvac apart to clean it once or twice a week so after some research and experimenting I brought a dust deputy cyclone and 30 litre collection barrel from here
http://www.toolovation.co.uk/category_s/125.htm This has made life a lot easier as all I need to do is unclip the top of the barrel and empty it which takes about 2 minutes and I only need to check the Camvac filters every 3 or 4 times I empty the barrel, even then there is only a small amount of dust in it and the suction does not noticeably drop at all.
Below is a photo of my system
John