Tarp pole mod question

[KMACK]

Looking to make a DIY pole mod (poles over the RL) for my WL Bigdaddy. My question is how long should the poles be? Do I need to lay the tarp out and measure from one pull out to the other and add a certain amount or go with the actual measurement?? Thanks!

[Dweller7]

I bought my poles here: http://questoutfitters.com/tent_poles.htm#TENT%20POLES... Two #4081 and four of the #4080. Total length is 54 inches plus knocks. Used 6" shock cord loops larks headed to pull outs.