Definitely stand in your boat and roughly figure it out. That's what I did.
Another tip. The install manual for mine said to set the straps at a 45 degree angle... That's more for the front ones. I set the back ones that way and it definitely restricted the fishing area off the sides in the back. The boat luckily had hardware for the bumpers that caused the straps to be perpendicular (instead of 45) to the side of the boat and it holds just fine that way.
Also for the front straps, if you can (and it's close to 45) put the hardware into the metal of your windshield. I wish I did. I chipped the glass a little tightening the screws. It'll work just the same.
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