Small piece of advice IMHO. If/when you COMPLETELY extend bis, remember all the stress(weight) will be on your TENDON, and not your muscle. Muscle strength> tendon strength, so your bis can handle "safely" more lbs. than your distal tendon. Trust me on this, as I partially tore mine doing fully extended straight fixed bar preacher curls in 2006 and it finally just completely tore last month requiring surgery. If I hadn't of been fully extending with "heavy" weights, then I don't think I would've hurt it the first time back in 2006. Since 2006 I always trained bis lighter and cautiously but it tore working back.
My advice would be DO NOT fully(arm completely straight) extend with your "heavy" sets but maybe on lighter sets as your tendons can more safely handle somewhat lighter weights than your bis(muscle) This is just my opinion. Hope this helps.