Not 100% sure but I think the max argument size in 3.2 was/is 32000 bytes as I have a note in the source code of DFQ saying:

Set_Argument_Size 32767 // It might be wise go bigger but WIN32CM does not allow this.
Remember that DataFlex 3.2 was created over 20 years ago and memory wasn't available as it is now. So don't try to use this old product for modern solutions. Think about migrating the project into a Windows or Web project using the latest 19.x product. Yes, I know it won't be easy but it will not be easier in the coming years and there will be a moment in the future where you cannot continue using the 3.2 product because of changes by others (Microsoft, hardware etc).