Serial tracking - UOM change

We produce some parts that require serial tracking and have been doing this manually up to now. I have been exploring the serial tracking abilities of Epicor and have been able to successfully test this function on new parts. 
The problem arises if I would like to try and serial track an existing part.When checking the track serial numbers checkbox, an error comes up that the indicates the parts inventory UOM allows decimals. The UOM for this part is the default UOM for most of our products but there are many times that decimals are required throughout various purchase/inventory transactions so we would not want to change it to disable allow decimals. (In the test on new parts, I created a new UOM that does not allow decimals)
I have tried adding a UOM code to the UOM class and can change the sales and purchasing primary UOM but am unable to change the inventory UOM
Has anyone experienced setting up serial tracking or know of a way to set this up on existing parts?
 
Thanks
Debbie