If a blind man can show a deaf man how to aim and get kills with the 5in AA guns... think of what the 88mm can do. 
That's because the American 5" guns were proximity fused. To my knowledge, the Germans never developed proximity fuses. The 88 was time-fused using a Kommandogerat optical predictor to determine the azimuth, slant range, elevation and time setting. In fact General der Flakartillerie a. D. von Renz estimated that in actuality it required 4,000 88mm shells to down one bomber. A USAAF study (trying to find it) indicated that were the Germans to use proximity fuses, 8th AF flak losses would triple and the B-24 would be knocked out of the European war entirely.
In contrast, the American 90mm AA gun, and I believe the British 3.7in AA gun, did have proximity fuses, as well as greater range, and were much more effective. The downside being that the Allied weapons were heavier, less mobile, and produced in far fewer numbers than the Flak 88.
