I use both subtrim and adjust the linkages. Subtrim doesn't affect the the EPA settings, that's the beauty of it, normal trim does however. I put my steering horn on as close 90 degrees as possible and then adjust it to 90 with subtrim, then I adjust the linkage to get my wheels centered while making sure the two steering arms are equal length. Last step is adjusting the EPA, I hold the steering at full lock and add EPA till the servo starts buzzing, then back off till it doesn't buzz anymore. This gives me the most amount of steering without overworking the servo.