Hi DM, Thanks for the info and links.
I guess it all boils down to the what you use the bars for and how much weight is an issue.
I have never heard of any structural failures of the original CW Mini-Bars used on Clelands since 1982 and these were similar in terms of size construction methods, gauge and grade of aluminium alloy used.
However, with so much of the riders weight over the rear wheel, Clelands are very different dynamically from most other off-road bicycles. With a Cleland the greatest structural load is probably during out of the saddle climbing as you pull hard on the bars with every pedal stroke. Whilst using this technique you can easy to pull arm or shoulder muscles. If you ram the bike into something immovable then the the bars tend to rotate in the stem clamp instead of bending and any dynamic loads are greatly reduced because of the very low pressure tyres.
As for bar width there is no point in having wide bars on a Cleland as the tyres are so soft and squidgy that the front tyre has to twist beyond 60 degrees before any noticeable torque is transmitted through to the handlebars. Also, wide bars wouldn't easily fit between narrowly spacs trees etc.
This is not to say that you don't have a point in regards to a heavy and aggressive rider fitting these bars to a standard mountain bike. In such a case, tougher but heavier steel bars could indeed be safer.
