I have a 2008 Heartland Razor 3110DS and RV shop says my springs are flat and need to replaced. I currently have 6000lb Lippert axles with 4 leaf springs. Shop says for this toyhauler he recommends at least a 5 leaf. Any brands, specific place where you guys have purchased these upgraded springs. I'm in the Dallas, Tx. area. Thx. LR.