We had a CFII and a 135 carrier pilot wash out. We had CFIs and helicopter pilots get through just fine. Don't put yourself under an umbrella that groups a ton of different people that shouldn't be compared. I know plenty of great CFIs who don't have the other I, and would do great at indoc. I also know MEIs who I doubt would make it through due to their work ethic. Depending on where you go, as long as you aren't afraid to seek extra help when you don't understand something, they'll help you out. Just study, study, study. Know your flows, limitations, and memory items. The rest will come...but if you show you can't put forth the effort to memorize the easy things, it'll be a long road.