I don’t know how you came to that conclusion. There are two steps to get the alternate approach using an iframe working. You skipped step 1 and went right to step 2. That didn’t work, because you skipped step 1.
At this point you have all the information you need to get this working with iframes. Since further questions are probably going to be about writing the HTTP endpoint or using an alternative mapping solution, you should probably start a new topic for those questions.
Best of luck.