DDK - Die Deutschen Klassiker

I am making a new cable to run from the battery on my starter motor in my 914. This was missing when I stripped the car so cannot check the cross sectional area of the original cable. Can anyone confirm whether this should be 16mm2, 25mm2 or 35mm2? If I choice to go for a larger sized cable, there is obviously the upside of a greater cross sectional area. Is there a downside?

I don’t know the factory spec but 16mm2 is too small. The starter motor needs around 150A but for a short period. 25mm2 is rated 170A but would be derated due to length. It may get a bit warm if cranked for long periods. 35mm2 would be a safer choice, the only downside being it’s extra weight.

I don't know if this helps Phil but here's a photo of my new loom. I've tried to show multiple thickness wire to help illustrate the size of the starter cable. The thickest red one in the photo being the starter cable.

FWIW I went with 35mm2, which my supplier said was rated at 240A.
It fits through the holes and is flexible enough to make the run, so as Jonny says the only downside is weight.

Thanks all, 35mm2 it is!