The lower shrouds on my Col. 43 are essentially U-bolts - they are a stub of stainless strap welded to a large stainless plate which acts as a big backing plate - the stub passes through the deck like a conventional chainplate. All the uppers are conventional long straps bolted to bulkheads etc. It has kept a 66' stick standing for 42 years despite years of serious neglect and the boat has sailed from N.Y. to San Francisco so I guess it's adequate.
I've never, to the best of my knowledge, seen a chainplate perfectly aligned with the shroud attached to it - that's the reason for toggles.
??? Really? Hmmm, perhaps you need to come back to the East coast, and have a look at some Proper Yachts... (grin)
Toggles are best used for dealing with variable and eccentric fluctuations, such as those due to things like headstay sag, and pumping... They are certainly not intended to correct to sort gross misalignment I was referring to...
Not sure I completely understand your description of your U-bolt arrangement, but there's no question a U-bolt can be made strong enough
for a particular application...
My problem with U-bolts that I see on today's boats, is that the clevis pin will be subject to point loading, rather than having its load distributed over its full diameter when held captive within a properly sized chainplate hole.
I doubt there are many riggers out there who would consider a u-bolt attachment superior to a proper chainplate, and that's one reason you'll never see u-bolts in lieu of chainplates on boats built by Swan, Perini Navi, Royal Huisman, and the like...