Speeding rational up could be done as well, but the original question was is there any interest in a rational that optionally supports over/underflow checking. As mentioned previously, the new template parameter would control if the checking code were generated, or the original implementation. The original implementation would be great for Multiprecision integer types, and in fact, the checking code should be prevented from being used if the integer type is Multiprecision (type trait checks would be used to insure this). I'm ready to submit this code (or code change), make changes/fixes, update test cases, etc. but what would be the proper channel? Via the sandbox area?, post a big diff? The last discussion I saw on rational was on about 12/12/04, so there is the question of a current maintainer in the mix as well.
If there was a current maintainer, then filing a ticket or contacting them direct would be the way to go... as it is I suggest creating a modified version in the sandbox - I suspect that if you want to get a big-ish change accepted then you're more or less going to have to volunteer to become the next maintainer as well. Sorry! HTH, John.