Juan
Eso lo intenté explicar yo de cómo pasaba en: https://igpmanager.com/forum-thread/64484
Yes you can, You have to be a client.
Clients can improve the chasis they get, suppliers only supply. It might not be intended this way, but it's how it is working now. I guess it needs to be fixed. Since at the moment:
If you provide chassis: You get the benefits from clients a % increase in research and an extra DP point for each customer plus some money.
If you are a client: You can improve the chassis with the chassis points.
If you are both, you can only improve the chasis, at least it's my case as I became a client after being a supplier. My supplier perks are gone, but not my clients.
This is what I see:
When I was a supplier only, I had the benefits of a supplier, +8 DP +8% research and some money I think, they disappeared once I became a client too. Because I thought I had to, in order to improve the chasis, I was just trying out the feature.