well i do hunt. I shot that round using an IC choke with 7 1/2.
Your first effort at 66% wasn't to bad at all ! I'd be tempted to stick with the same choke/shot size combo ... and expend your efforts in the sporting clays "learning curve" by improving on your mechanics, (especially consistant gun mounting if you're shooting "gun down" ) learning to better read the targets,( for line, speed, & variatiuon... are they dropping or rising, crossing or quartering, fading from one side to the other, etc.) establishing more effective "hold points" to allow you to get on target more efficiently and smoothing-out your swing. At first the targets may seem incredibly fast (just like a High 2 Skeet target does to a right-hander) but in reality, most are quite hittable once you learn a bit of technique to do so.
Just like 1H, 2H, 6L and both 8's in Skeet, quite a few sporting presentations are more akin to "learned" shots than simply the techniques most often encountered in field shooting. Incoming droppers, springing teal, rabbits, battues/chondelles and various high tower targets can give first-timers (and many experianced shooters) the fits until they "learn how". Once you've developed sound mechanics and a repetoir of target types and presentations, scores will improve. Station-to-Station and week-to-week with frequent course changes, and from Club to Club, sporting targets vary considerably, and are far from the more defined target lines of standard Trap and Skeet layouts.
Don't get discouraged, don't be afraind to try & adapt to new techniques if your not getting results, and by all means, shoot lots. Initially, a round of 50 will highlight some problems, but rounds of 100 will at least let you work a little more on these problem target presentations. ( For example, 2 hits on a Station of only 4 shots doesn't really let you learn much [and even less for a single hit or " straight gooseggs"], but the ability to try 10 shots on the same station will at least confirm where and when you need to adapt. Once you're averaging 7's and 8's on each station, you'll be well on your way.)
Good shooting ... the fun seems to happen by itself !