Mike,
Veeduber recommends that one drill with a #40, deburr and then dimple
with the 1/8" dimple dies. I have done some like that and some using
the #30 drill first. Sometimes I have to 'open up' the hole a bit with
a reamer when trying to put in the rivet when I use the #40 bit first.
Veeduber's advise was in reference to using blind rivets iirc.

The springback dimple dies are meant for dimpling fuel tank skins so
that smearing sealant will not make the rivet stand proud of the dimple
so I think they may be a few thousandths oversize.

Hope this helps and remember all advice is worth what you paid for it!
Bruce