I just did this.
I got some 1/4" aluminium sheet and some 3" channel.
I cut the channel to the length of the jammers, they were 3" wide so that worked.
I cut the plate to the right length and about 8" wide then bent it to the profile of the mast using a hydraulic conduit bender.
I cut the channel down so that it sat on the crown of the bend and welded it to the plate.
This gave me a flat surface for the jammers about a 1/2" higher than normal.
I tapped the aluminum
channel and plate to connect the jammers.
I used a rivet with an internal thread to put threads in the mast.
I screwed the whole shegan to the mast.
My thought is that this will reinforce the mast rather than weaken it.
No pics but I can post some next week if you are interested.
You just have to promise to not laugh at my Shreck welds.
Shreck = strong but ugly.