Great tips! I had the wing hinge snap about four years ago on my Flight 19 Avenger (same number FT-28 too). Eventually I decided to glue the wings in place and fixed the sag issue, just like you. In retrospect, while I appreciate 21c trying to accurately re-create the Avenger's complex wing folding mechanism, they either should have provided more internal support and robust tabs to hold the wing in the correct shape, or just gone the inaccurate route and made a sturdier hinge, like BBI did with their Hellcat.
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And on another note, 2016 marks the 10th anniversary of the release of the 21c Avenger
![Very Happy :D](./images/smilies/icon_biggrin.gif)
We waited two years for 21c to develop them after their initial 2004 announcement, then had the anticipation of the preorders only for them to show up at Walmart for a then expensive $75... And they had sagging wings and missing screw caps
![Mad :x](./images/smilies/icon_mad.gif)
I remember driving all over my area in Central California coming up empty handed, only to find them while out on a road trip. I never, ever, saw the Avengers at any of the Walmarts in my area. Eventually my local Hobbytown USA store got some in, so it wasn't completely a lost cause...
The Avenger was one of 21c's most ambitious 1/18 scale efforts, but it suffered a lot of QC problems that at least to me, kept it from being one of the best 1:18 planes ever made... Still, I've got four of them, including one still boxed
![Cool 8)](./images/smilies/icon_cool.gif)