I found a way around this that works fairly well. I added a 'non-enterable' row number at the begining of each portal row (@@) and increased the row height and font size sufficiently for the user to tap the row number. This selects a specific row in the portal but also activates the portal scrolling. The user can then swipe anywhere within the portal, up or down from the selected row without using the scroll bar itself. The user can also reselect another row if needed.
I used the portal row number simply to avoid accidently tapping an editable field in the portal row thereby opening the keyboard.
That is a good tip. In my specific implementation, I would prefer not to go that way. I am using these portals only to allow users to select a record to see on the other side of my layout. As such, none of the field information within the portal itself can be edited within the portal. That keeps me from having any concern about the user accidentally entering data. Placing a non-enterable row number within the portal itself is a little less user friendly. Users will need to know what the number is for, and that they need to tap the row number to enable the scrolling. I just don't want to have information displayed in the portal that isn't intuitive to the user.
Perhaps Filemaker will address this in furture releases. Scrolling is such a common record scanning technique that they should be considering how vertical scrolls translate to the iPad and FileMaker Go. The narrowness of the vertical scroll is problematic as users have to tap repeatedly to activate the scrolling. It would be nice to have FileMaker Go know this is a scroll portal and have it scroll like other iPad apps. Rather than users being able to simply touch scroll, they have to find the right spot to enable scrolling. Even if the vertical scroll was wider (which we can't seem to address), you still have to tap it to activate the scroll, then scroll - at least a two step process. Instead, FileMaker Go users should be able to flick-scroll in these portals just like other apps.
You don't have to tap the scroll bar at all to activate scrolling. Since all your portal fields are not editable, just tap anywhere within the portal and then flick-scroll up or down.
Forget the scroll bar; you don't need it.