Our SJ21 came with similar triangular boom-end sheeting system. I hated it for the reasons you describe: it makes getting to the stern awkward, there's tons of friction, and you need about 45 ft of line, most of which ends up piled in the cockpit when close hauled. Requires many armloads of rope to move the boom. No vanging or boom control on deep headings. Two foci with a running fiddle on the boom means the boom end travels along an elliptical, rather than a circular path -- so the boom tends to slat back and forth more than a 1-point mainsheet system in high winds or swells. And worst of all: when deep reaching or running, a couple fathoms of mainsheet are draped thru the cockpit or hanging over the side of the boat. Guess what happens during an intentional (or God help us, accidental) jibe? All that messy cordage goes scything thru the cockpit, removing hats, tangling around necks, winches, the tiller, and so forth.
Oh, and the cleat was on the cockpit sole, way aft and directly under the tiller.
So this Spring, I moved it. We added a hard point -- a forged Wichard U-bolt
-- to the cockpit sole, just ahead of the tiller. It is backed below with an epoxied plate of 1/4" aluminum. Then we added a hanger to the boom, 30" from the end -- one of these
, to distribute the load without needing multiple blocks.
In between, we used two inexpensive 50mm Lewmar Synchro fiddles
, the lower with cleat, becket and stand-up spring. These worked with our existing cordage -- tho we were able to lop 20' off the bloody mainsheet.
The upshot: with less friction and less leverage on the boom than the old system, hand-playing the mainsheet in high winds takes more effort, and we have lost some leech tension close-hauled. But I can now sit forward or aft of the sheet, which makes singlehanding easier. The boom reacts more quickly to small adjustments on the sheet, and you can sheet-and-ease quickly for controlled jibes, without snagging on deck hardware or passengers. You can also just grab the whole mainsheet in your hand and guide it across. There's less line on the floor. And the mainsheet imparts some downward force on the boom even DDW, assisting the vang (which is weak on our boat).
It was a really nice upgrade. Took about 2 hours and $100, and no advanced skills were needed. If we want to add a mid-cockpit traveler later, we are ready for that. Still, I agree you should sail with what you got first. Maybe it will suffice for your purposes, or at least you'll have a chance to consider alternatives. Cheers!