Marcus,
I guess you are right...they equip the expensive metal in leather strap and steel in steel bracelet....this is their normal practise i guess..
5712 are may be compatible,even if you get the steel 5712 its should fit well with the rg/wg provided leather starp,but it will be a problem looking for the buckle!
5980's case is thicker and currently,they are still no wg or rg version out,therefore leather starp is totally out of the question...
I hope i answer you correctly.Thanks.
BHK9.
For your addtional info,

