I have a rope with a snap clip that I attach to the forestay. I run the rope around the winch drum on the front of the trailer. I climb in the boat and raise the mast and pull the rope fairly tight and tie it off on the jib cleat on the mast. I can climb out of the boat and hold the forestay...
I don't think the Capri 14.2 mast and mast mounting system can handle the weight and load of trapeze. I used to have a Solcat 18 cameraman that was setup with twin trapeze on each side and the mast and mast mount are a lot stronger plus the boat had 220 sf of sail area with a 28 foot mast.
It looks good but it look like it's mounted a little far out on the tiller so that when you turn the tiller it will get a lot of slack. It should be mounted so that the arc is the same when you turn the tiller from side to side. I had to adjust my mounting point on my tiller for the same reason.
It holds the tiller in position so when you sail single handed and you have to move forward in the boat to adjust the jib or other things that when the boat rocks from side to side the tiller and rudder don't move back and forth and a possibly you to capsize.