This is not a good plan, I'm afraid. I think a 29,000 row XML file will make your form very large, and that a dropdown with 29,000 options would be unwieldy for users. I think instead you need to consider ways you might structure this data in a SharePoint list that would allow you to offer some filtering. Not knowing what this data is, I can only suggest some guesses - but perhaps you could categorize these entries, and give the user a "Category" dropdown first, with limited options, then filter the query for the "Very Large List" data based on the selected Category. Even if you stuck a column in SharePoint for the first letter of the option and let the user initially select from A - Z to narrow down the data returned to the dropdown, it would help.
Hilary Stoupa
