When mixing built-in custom fields and a Proforma form the attached form is always rendered at the bottom. Because field order matters we tend to solve this by only using Proforma fields and link some fields to custom fields. This doesn't work for the attachment field though since that field is not supported and that means that the attachment field always has to be rendered at the top of the form.

That is bad form design and it could be alleviated somewhat by having an option in the form builder to place the Proforma form first or last on the screen. This should preferably be possible to set individually on each form.