The 150 is 26Gal total (13per side) but only 22.5 is usable. The POH is the go to source.
If you fill your tanks to the bottom of the filler neck and measure with the tube you bought from Sportys and it reads just over 11 gal in each tank then that is usable. If it reads 13 each side then it is total and you need to subtract 1.75 each side to get useful amount.

Ron Stewart
N5282B
KSFZ


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