He was probably right, moving the weight of the outboard backwards increase the lever and will lead to stern heavy behavior.
To the added lever there must be added the weight of the bracket too.
As smaller a hull is as more it will suffer from incorrect weight distribution and that is a common issue.
The added weight can be equalized with shifting weight forward (coolers, batteries) but most likely some additional weight in the bow area would be needed to counterbalance the added weight on the transom.
Honestly I would not do that except I have to.
Chris