Very good to know, thanks for taking the time to post it up here.So this took me awhile to do, thru trial and error, and trying to to get information from people and companies who do not want to give info...in any case, here's the finished product.
Things to note if you're trying to replicate this:
-why did I do this? The semi-dovetail on the Romeo 1 was a joke. The Leupold DPP offers a rear iron sight you can mount and co-witness
-slide was milled about 2mm in the front end to accommodate the Leupold DPP. The good thing is, the rear and the screw holes are identical between Romeo 1 and DPP
-thread pattern for the Sig holes is 6-48 UNC. You can't find these screws at Home Depot or Lowes. I got kind st a Brownells
-Front sight is Dawson Precision 0.44" fiber optic. You can probably get away with 0.40".
-Springer Precision has released a mounting plate so you don't have to mod your slide. I talked to him while they were designing and manufacturing the test plate, and it's very promising.