If you are going to fix one end of the spring, "cone" the other if it gets too loose, otherwise let it hang free. Placing an "edge" of pressure on the both ends of the spring is asking for trouble and will only rip whatever restraining measures you have taken out. There are going to be some impressive leverage forces at play once you start flexing up. 1/4 inch would be OK if you only fix one end, ie, no tension applied to the 1/4" bolt.

Take care when drilling or opening out any existing holes in the chassis as this can weaken the chassis at critical point along its length. Specifically do not drill through to the other side unless you are going to weld a crush tube in place. (example of a crush tube can be found where the steering box mounts to the chassis)

2002 Sporty , Ironman 2.5" spring, 2" body, 15 x 7 ROH wheels, K&N, 15 x 10.5 Simex Centipedes, Powerchip 91.

"Never argue with an idiot. They will bring you down to their level then beat you with experience!"