MLG TAXIES ONTO WT RESTR TXWY.

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TAXIED ONTO A WT RESTR TXWY. WX WAS HOT AND HUMID AT 80 DEG F; PERFORMANCE WAS A FACTOR AND THE FULL LENGTH OF USABLE RWY WAS MOST IMPORTANT. THE NORMAL RWY WAS CLOSED FOR CONSTRUCTION WHICH WAS THE LONGEST. BEING FAMILIAR WITH THE ARPT WE DID NOT HAVE THE ARPT DIAGRAM PAGE IN FRONT OF US AND WHEN GIVEN THE OTHER RWY WE INADVERTENTLY TAXIED TO THE VERY END UTILIZING A SHORT TXWY THAT WAS LIMITED TO 50000 LBS; 79 FT WINGSPAN. OUR ACFT WAS 77 FT WINGSPAN AND SLIGHTLY OVER THE 50000 LB LIMIT. THE DISPLACED THRESHOLD WAS STRUCTURALLY SOUND FOR TAXI AND TKOF. BEING DISTRACTED BY PERFORMANCE AND TKOF DISTANCE CONTRIBUTED TO NOT LOOKING AT ARPT DIAGRAM. BEING JUST OVER THE WT LIMIT POSED NO SAFETY HAZARD WHATSOEVER AND OUR WINGSPAN WAS NOT A FACTOR. SOLUTION: THIS IS A PERMANENT STRUCTURE ON THE ARPT SO WHY NOT HAVE A PERMANENT SIGN STATING LIMITS? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THEY FLY INTO THIS ARPT FREQUENTLY AND ARE VERY FAMILIAR WITH THE ARPT. THUS THEY DID NOT HAVE THE ARPT DIAGRAM ON THEIR LAPS. WHEN RWY ASSIGNMENT CHANGED THEY FIGURED THEY COULD MANAGE. OBVIOUSLY THIS WAS NOT THE CASE SINCE THERE WERE WT RESTRS. THEY PROBABLY SHOULD HAVE TAXIED ON TXWY Y5 INSTEAD OF TXWY Y6.