[AusF20/F48]

I think it depends a lot on the gas pressure in the strut
The standard strut is about 435 Newtons.
I could get the same length in a 490 N version for $49.00ea
My concern about the length of the spring was the distance between the strut body and head when the strut was compressed. It only gives around 22.5mm. The max compression of the 25mm spring is at 14.5mm + 6mm for all the washers= 20.5mm which is under the 22.5mm, so no real additional stress on the strut.
I was concerned that the 32mm spring only compressed to 19.20mm so when you add the washers it could have the potential to generate too much tension on the strut and bracket.

My thinking was I rather try thicker rubber washers (as they will also compress) with the 25mm Spring than risk the compression. If needed, I would have got the higher rated struts.