I'm building a minimalist 20 ga single barrel.  I have an old Magtech 20 with a modified fixed choke.  Im going to have a gunsmith ream and tap it for browning invector chokes.  I don't want a super tight pattern.  Just a good even pattern at 40.  I will be shooting LB ##6 and TSS #9.  1 5/8 oz loads.  what choke do you recommend??