The main points already mentioned were right on. Don't use a vise base. The mini is already cramped in Z and those things just contribute to a huge loss of rigidity.
We have two Mini Mills that have "Bock" Sub-Plates on them.
You really can't beat these for quick set ups. I strongly suggest you consider one. (or make your own steel one) They will custom make them for you. We ordered ours extra long to extend all the way to the right edge of the table, over the chip/coolant cavity to keep the rotary table out of the way. (What's a mini without a fourth?) The HRT-160 Rotary Table mounted on the X+ end stays on all the time.
They have a choice of two vises. One is a Kurt 6" for the bigger mini stuff. (Damn good vise that does not kick up) The other is a "Bock" Twin Vise (4 inch) for higher production and smaller stuff. (The really cool vise) You can also carve you fixtures right on top of special snap on plates that fit right on top of the vise in place of jaws. Get soft jaws and carve them to whatever you want. I program a lot of "1st Op. in one jaw and 2nd Op. in the other jaw" things. OR both jaws doing the same thing on two parts.
With the sub-plate everything is doweled into the same place every time. You can almost throw you edge finder in the trash.
You could even hard coat your work coordinates into the program using G10.
Here is another cool thing to do to a Mini. Look in an Enco Catalog (don't laugh
) for a "Bison" 5C Collet Chuck for about $230. It works just like the regular 6" chuck for the rotary table
(T Handle and Scroll) but it holds 5C collets. Make a faceplate for the rotary table platter that has the bolt pattern for the Collet Chuck and the 6" Chuck. You will also need to make an adaper for the collet chuck so the Locating Diameters are the same for both. (It's just a ring about .150 thick.) Press this adapter into the collet chuck so it doesn't get lost. Now you can quick change between collets and 6" chuck. DO NOT buy the Haas Chuck. Do your own planning and reaserch and you'll be better off. If you want I can give you the numbers of exactly what we bought and a sketch of the faceplate and adapter.