</font><font color="blue" class="small">( Past experience has been that the bolts going through the bucket when attaching things like toothbars or forks cause the holes to oval out from the stress and deform. I think that is why Markham gives the extra metal plate for their toothbar. I recommend that for heavy use the metal around the bolt hole be brought up to at least 3/8" for tractors up to 25 HP and 1/2" for anything over that. The metal stiffeners should be welded... not just relying on the bolt to hold them in place.)</font>
Well, my toothbar has a 3/4" bolt on each side. I installed it with washers between the bracket and the inside of the bucket. I have extremely, and I mean extremely, over abused the tooth bar to dig up roots, rocks, shrubs, concrete slabs and a few small stumps. The bar is as tight now as it was when it was first installed. It has not ovaled the holes or moved even a 1/16". The 60" Kubota HD bucket has not been deformed in any way. The teeth themselves slip over the bucket cutting edge thus adding more strength and support to the entire toothbar.
So, based on my experience, and that of plenty of others here on TBN, your recommendation seems like big time overkill. I can't recall anyone who has a tractor over 25 hp who has added a 1/2" or even 3/8" stiffener to their bucket around the toothbar mounting hole. I would guess that your recommendation is valid only if you have a really cheap, thin walled light duty bucket. As always, your mileage may vary.