Hi Thomas: Thanks Thomas, you just made me feel better , knowing I’m not the only one that ever happened to. I’ve placed an order from Dwyer with the specs below.. DM-6 Mast Extrusion - Tube Length 21 ft. 5 in. with Sailfeed at 2 ft. 8 in. (which is where the full width of the sailfeed is – not where the taper begins (taper begins about 1 inch lower). length is per MSOG copy of 1986 brochure mast length spec. I measured my mast at 21 ft. 4 in. 1975 M-17 hull 69 (not coyote with the flush deck) , also saw length of 21 ft. 6 in. per Mike Leonard, '83 M-17 #369 . Again, going with the 21’5” unless someone from Montgomery owners forum or at Dwyer suggests I should go 21’ 6”. Is there a need for me to measure my mainsail which came with the boat? or to determine the boom height? Haven’t set boom up yet so not exactly sure height or how it attaches to the mast. fyi: ?Bob? at Montgomery Boats said to talk to Joy at Dwyer Aluminum Masts when ordering spar for the M17. Thanks, jim