This may help...but I still would upgrade the springs, especially if you intend on racking up the miles on the set-up.

https://ls1tech.com/forums/showthread.php?t=327734

 

Imo it is better to over build something rather than be on the edge of braking something.. Just my .02. I would sell the 918(if you have them already) and take that money and just do it right the first time. Also i think the 918 would wear out quickly. I would go with a dual spring if i was you. Like someone said before a broken spring can be the end of that motor you just finished building.