I tend to agree with Eric, but unfortunately he hasn't made a comp for my Tanfoglios yet so I'm stuck drilling holes to make up for subpar comps!?!
The Tanfo V12 Gold Team is the extreme example:
Two tiny ports in the comp and 12 holes to make up for it. It takes 8-10% more powder to make the same velocity as a barrel w/o holes. It makes sense to me you get the same downward force from one hole at 12 o'clock as two of the same size at 45 degree angles to one another with half the powder loss. I tested this with my custom "Y7 Gold Team":
I'm pleased to report it shoots flatter than the V12 and uses less powder (3-4% more than a barrel w/o holes).
My best comp so far for Tanfoglio is this modified three port on the left, to which I plan to add 3-4 holes at 12 o'clock:
I own a dozen Open guns, have shot a lot of comps, and have opined the only advantage to V pattern ports is looks and maybe a little less flame in your line of sight. Any holes I add to my guns go straight up from now on.