[IC27A] Sling Points, Cat 27

[gagcca]

Hello, I recently purchased a 71 C27. I've asked the yard to pull her so she 
can get the bottom power washed. The yard has asked if she has sling marks (so 
they know where to place the rear sling, so they don't damage the prop/shaft - 
I'm asssuming). Could anyone here provide some advice? Is there a measurement 
from the real transom that they could use? Many thanks. Matt