spring question

I am about 85% done building my e-revo and thought I was good with springs. as a roller it sat so high I was worried that it would be too stiff. After installing my neu 1515 and adding a 400g weight to the battery tray to simulate close to rtr weight it almost bottoms out just sitting on the floor, even with the collars tightened all the way down.

I have the teflon coated GTR's, 60wt in rear, 50wt in front, white springs on front and green on the rear.

I do not want to spend a fortune on springs trying to figure this out. What are some of your guys recommendations for a high speed high flying basher?