Measuring in a straight line - 27" from c/l of exhust port to end of can body --leave 3" more for a turn down stinger addition -I use the old molded silicone rubber ones (large) .I forget the brand but they are still in hobby shops
10 lbs -1000 squares is about perfect- the extra pound and another 150 squares is about the limit
My 260 was very good n smooth but not crisp n quick like my Showtime using exactly same setups