Thru-Bar Spreader Bases

[Douglas]

Has anyone had experience with the Z-Spar "thru-bar" spreader bases, causing a mast wall failure ?

One rigger says : " We do not use through-bar technique for spreaders assembly as this creates too large cut outs in the mast section. I have a recent example here with a brand new production mast snapped at the cut outs level."

An example of this "thru-bar" detail can be seen at : http://www.zsparsuk.com/mastpic007.jpg

If I do choose to use this "thru-bar" spreader base system on my new mast, would an internal sleave reinforce the mast wall, to offset the weakening of the mast wall due to the large horizontal bar cut out hole ?

Douglas