Brian,
One problem.
8.5 pounds is NOT 8 lbs 5 oz. It is 8 lbs 8 oz.
8.5.5 pounds is not 8 lbs 5.5 oz. It is 8 lbs 8.8 oz.
The only way, IMHO, that the weight is ever going to work well, given that we live in America and America is always right, is to have three columns:
10.5 lbs 10 lbs 8 oz and 4.77 kg
Entering any amount in any column would automatically populate the others. This is because some people use scales that measure in decimals and some in pounds and ounces and it is a hassle to convert these in your head or by a written chart. Certainly, a scale which states 10 lbs 9.5 ounces will be difficult to convert to a decimal. And, the same for when you get 10.2 lbs, you don't want to figure the second column. And, 4.77 kgs would be a mind teaser to convert off the top of your head to the other. It is also nice to sit at the computer and tell the parent(s) that their baby weighs 10 lbs 8 oz since they live in America.
The final reason is you want three columns populated each time so you can see three columns of data each time no matter which was entered. There is nothing worse when you have a FTT baby then to print off the VS, and see:
kg
lbs
lbs
kgs
lbs
kgs
**Any reference to living in America was simply to refer to we are just about the only ones who do not use the metric system.
