In my never to be humble opinion, I would go ahead and get a full choke. NOTHING less than IMOD. If the day comes that you want to sell or trade and it has a more open choke, you will regret your choice.
If you have barrel work done, Tom Wilkerson, Kerry Allor or Heritage Gunsmiths. Keep the receipt and you will usually get some of your $$$ back. Anybody else, you will get less for the bbl. Tom Wilkerson now does removable chokes. They are expensive but they are good.
.020 Choke with 1 1/8 oz 7 1/2 or 8s will give great breaks. The above usually have handicap chokes of the low to mid .030s. My Allor O/U barrels for doubles is choked .020/.030
As long as we are on the subject will someone please list approximate contrictions of standard choke terms XF,F,LF,IM,M along with the digit numbers used. Example .035 F #10. Asume a .740 bore. Thanks, gyrine
Here's the figures I've used as a rough measure of choke constrictions for a 12 gauge:
Skeet = .005; IC = .010; Light Mod = .015; Mod = .020; IM = .025; Light Full =
.030; Full = .035; X full = .040.
Subtract that from a .740 bore, and you have your inside diameter.
Hope it helps. John