Dear Greg,
SAM does not limit the DC/AC ratio, so you can model as large an array as you like for a given inverter.
I would recommend using the "Specify modules and inverters" option on the System Design page to ensure that you model the system as you intend. The "Specify desired array size" is a good way to get started sizing the system, but as you note, may not be able to assign the values you want for modules per string, strings in parallel, and number of inverters.
If you would like me to review your SAM file please either attach it to your original post above by editing it, or email it to me at This email address is being protected from spambots. You need JavaScript enabled to view it..
Best regards,
Paul.