you mean like this...
...and then like this...
? Not fragile, so long as you don't drop it off the top of a building or something.
Have you already soldered the wires to the board?
Me, I would mount the 220's to the heatsink first, then solder the wires to them after tinning the pins and wares(the heatsink will hold them still), then solder them to the board starting in the middle of the line, or from one end to the other. Whichever is more comfortable for you.
It prolly wouldn't make any difference much if you did all the soldering first, and then bolt them to the heatsink.