Probably the favorite argument of those who hold with a mid-Acts dispensational dividing line against those who hold with the Acts 28:28 dividing line is that we teach two bodies. They get this from comparing Ephesians 4:4 with I Corinthians 12:3.

Ephesians 4:4. There is one body and one Spirit, just as you were called in one hope of your calling;

I Corinthians 12:13. For by one Spirit we were all baptized into one body—whether Jews or Greeks, whether slaves or free—and have all been made to drink into one Spirit.

Ephesians 4:4 says there is only one body, yet the believers in I Corinthians were baptized into one body. If I Corinthians is not talking about the same body as Ephesians, then there must be two bodies. So, those who argue this claim, Acts 28 dispensationalists must teach two bodies.
This idea that we teach two bodies is an idea that they would like to pin on us, since it is easily dismantled. Yet few Acts 28 dispensationalists are so foolish as to fall into this trap set for us. I cannot speak for all Acts 28 dispensationalists, since I know many would not argue the same way I will on this. Yet these are my thoughts.

This argument is based on a misunderstanding of what the Body of Christ is. Since most dispensationalists seem to proceed from the idea that the word “body” in “Body of Christ” means a corporate body of believers, a definition that is an English idiom that does not exist in the Greek, they therefore come to this conclusion: that Acts 28ers are teaching a different corporate body of believers before Acts 28:28 from that after Acts 28:28, and thus are teaching contrary to Ephesians 4:4. But once we come to a proper understanding of the word “body,” and realize that it means the physical substance or essence of a thing, then we will realize that there can only be one real substance of Christ that is the source of that which those who enjoy a portion of what He is receive. There is only one Christ, and there is only one Body or Reality of Christ from which all who ever have and who ever will enjoy a portion of His Spirit have drawn all that they have from Him. Whether it was believers in the Acts period, or believers today, or believers in the coming kingdom, or powers in the heavens, or angelic authorities, or whatever it might be, all who receive what they are because of what He is are receiving a portion of His Body. This makes them in a measure what He is. This makes them Body of Christ. This makes them His representatives. There is no hint of two bodies here. Yet we are not the same company of believers that existed in the Acts period, or that the Corinthians belonged to. That is not a contradiction, because the Body of Christ has nothing to do with what company of people or heavenly beings are receiving it.

The problem is when dispensationalists, whether mid-Acts or Acts 28, start to define the company of believers today as “the Body of Christ.” They take this as a name for a company. Yet it is not. It is a descriptive phrase for those who have received His substance, and therefore have taken on His characteristics to a certain extent. There was such a group in the Acts period. Today those who believe have partaken of what He is to a certain extent, although I do not believe we will truly represent Him until the future. But there is no contradiction here. The reason there is one body is because Christ stays the same, not because there is only one company of believers who can be called the body of Christ.