Only thing I can think to add for missed popper takes beyond too big of a hook for little bream is that I may have too small of a hook gap for the bream to be hooked. If the popper is too large for smaller bream, I would use a smaller popper. If the hook gap is too small, I would use a larger hook or a smaller popper body.
Or the bream just grabs a part of the fly material (like a rubber leg or tail) and quickly swims off with it before other bream can get it without a solid take or bite (the whole fly is not in the mouth of the bream). This might be why some bream are foul hooked. For this problem, I don't know of a cure. Just the nature of the beast.
Sometimes bream are called smackers because they smack the fly off the surface when they bite. Never heard of or seen bream using their tail to slap the fly. After I cast the popper, I just give it a short line strip and let it sit. Sometimes the bites are very light (like a sip) instead of a loud smack.
I agree that sometimes waiting for the weight of the bream on the popper is good but I would be careful because if the bream have the popper too long, they could spit it out. Slack line has lost me bream also. Sometimes I have even had bream on a solid bite, good hook set, and with a tight line, and still have had them somehow work the hook loose and spit the fly. Stuff happens. Good luck.
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Robert B. McCorquodale
Sebring, FL
"Flip a fly"