Aside from its strength, for anyone considering making the Xootr Swift lighter by using another seatpost, the critical dimensions of any replacement seatpost for the Swift are its diameter and length. The two sections of the seat tube must remain on the same axis; there should be no wiggle or play that could translate too much stress to the seat stay, especially where it is welded to the seat-tube.

In a later production run of the Xootr Swift (not sure which year) the gauge of the rear triangle tubing was increased, as others have mentioned. The gauge increase would beef up the rear generally and make it more resistant to play-induced stresses; it would also offset the welding-induced reduction in strength of the 6061-T6 alloy in the weld's heat-affected zone.

I weigh almost 200 pounds and the Xootr Swift has so far proved a very sturdy lightweight ride. Mine has a short-travel CaneCreek Thudbuster with 33.9mm Ø extra-extra-long (507mm) post.

Regards
T