I agree, buying used masts may be abit risky, unless you know the person you are buying it from and that they take very good care of their masts.
So, perhaps a SW Joystick or the Powerex Z-Free (with at least a year of warranty)
would be the most cost effective/risk free way to go.
Where are you located?
If you are really a heavy sailor, the stiffer 520 cm IMCS 34 makes a little more sense, but I think you'll like your big Retro on the 490 cm a bit better.
Hope this helps,