I had this same problem. I now have C1 set to 5 which works fine for me. 

I used that large size. It had room to spare. 

Plastic is fine. 20 inch are easy to remove

Yes they fit fine, I prefer them. I asked Rad before I changed mine. They confirmed they fit.

I got mine from eBay here in the U.K. arrived real fast . I didn?t need to remove the tire, just screwed straight in. What bike ? 20 inch wheel. I will try to find the size I boaught.

I had the same problem with one spoke on the rear of my mini 4 that I replaced awhile ago. Thanks for the reminder, I will check the others.

Still in the same place as original controller on the mini 4. Not really the seat tube.

I have my 35 amp controller in the same box after water ingress problems.It?s  upright on the down tube of my mini 4. Seems to work well so far with no heat build up problem.

My 35 amp controller is hidden in a controller box. I went out a few evening ago with the weather forecast showing little chance of rain. I secured my bike outside at my destination putting the bag over the display and seat cover just in case. It rained fairly hard to my surprise.
On the way home at a leisurely ride, the bike started to fly along at full power and showing an erratic speedo. I got the bike under control by natural reaction of squeezing the brakes a little, this cut power to the motor as it should. This happened again further along making it difficult to manoeuvre  when turning at junctions.
  Arriving home I got off the bike and it shot off on its own with my trying to hold on to it. The front wheel climbed up the front of my wife?s car, with the bike almost vertical I managed to quickly pull it over sideways and apply the brake which cut the motor.    It was pretty late, I  don?t think anyone saw this happen but if they did they must have had a laugh at this old fella with the electric bike.  Little damage done just a few scratches to my bike. Next day the bike seems to have dried out and runs normally, I haven?t taken it apart yet to look inside the controller.
Still very pleased with the performance of this controller but it?s powerful  when it?s out of control
.

Mine started out just looking like condensation which would disappear when parked out it warm weather. It gradually got worse. Probably cheaply made, not sealed well when you consider it has hole in it for a usb connection. I now put a small clear plastic bag over it secured by a rubber band if it looks even remotely like rain or heavy dew.

You are wise to think about water effect to your 35 amp controller. I?ve had a couple of problems with mine. First problem the front light stopped working, looked inside to see the small lighting circuit board burned.  Second problem I noticed moisture in the display which progresses to slowly destroy the display. This is on a Mini 4.   Third problem to follow later. Water in the controller!

Hi Sergei, thanks for the reply. The XOD brakes came from Big Game Bikes. I?m pretty sure in our discussions Gareth advised I would need the long rear hose. It fits fine.
I understand the need to pack out/adapt the brakes to a bigger disk, just not sure if anyone here had done this. As you say maybe a floating disk would be a slight upgrade. Tony

On my Mini 4. I fitted XOD hydraulic brakes after doing the motor and controller upgrade.  I now need new brake pads . I notice I?m a bit late with this as my front Disc/rotor is scored.  I can replace this no problem but while I?m at it, is it advisable/possible to fit a larger disc/rotor.     Tony

Had this on my Mini 4. Difficult to find but a spoke on rear was broken at its bend going through the hub.

Yes they are a good swap and yes you will need the 20x4 tubes. I prefer this set up to the CST.