Here, for example, is a link to the part:
https://www.asraymond.com/standard-gas- ... GSNI515080 that shows a 15" length with a 6" stroke (so compressed length is 9").
Here is another site with the 6" stroke, but they only have a 60 lb strut. This might be a
bit low, but may still work ... the price is very good though:
https://www.rvupgradestore.com/Articles.asp?ID=298
But I have seen some other sites that seem to support your number ... so not sure now.
I would still try to get a 9" strut if possible.
Do be careful to get the GS
NI part (not some others that sound similar) ... that has a nitride finish for corrosion prevention.
The original OEM strut by Stabilus (expensive!) is that compressed length, although at a probable lower pressure of 65 lbs (290 Newtons), I believe.
Z