If you're wanting to mount accessories to the rear door of your tailgate T4 then you will most certainly need uprated struts.
It appears that off the shelf T4 tailgate struts only go up to 1250n in strength.
We worked with SGS a few years back to spec some new ones.
For our VW T4 Caravelle rear door with an alloy wheel and all terrain tyre we had 1400n ones made. I would suggest this as a good starting point. There is also an adjustable force strut available from SGS, which comes preloaded to a high rating and you can then let some pressure out until they work as desired.
When speccing the strut rating its a fine line between the door being heavy to pull down because you're pulling against the strut, and the door being too heavy to lift up as the strut isn't doing enough early on in the stroke. We found for our application 1400n ones were great.
(This information has been put together to help you find information on how to upgrade these components. We take no responsibility for what you do with this information.)