It's probably the spring idler tension pulley bushing get's wore and start's eating belts.As for a flex header there should be u-bolts to hold leaf springs under the table.If you take them off and jack up cutterbar and put u-bolt back on the other way it lock's the cutterbar to rigid. may also have to move reel up.As combine setting's go though the work Put in filler rod's in concaves if corn sieves are in,only run 9 knives on drum if saving it to bale,put solid small grain plate on top of concaves,make certain concave is close to the rotor and centerized.Take your time and set windboard and sieves and you'll do as good or better than any conventional out there.