Metabones speedbooster: is there any reason to get full frame now?

Here. I did not say that you used the word "only". I said that those are the only downsides you listed:

YOU: Here we have ignorance. Putting additional glass behind a great lens will create a different lens. The "punishment" for a telecompressor is a smaller field. A small change in total transmission loss. Greater weight.

When you accuse me of ignorance for my claim of loss of IQ, and say: "The "punishment" is...", you mean it is the only one. Otherwise, you would not put it in quotes, you would say "a punishment", and you would be more civil.