What is the maximum length for template field definition?

I am trying to generate mock data that replicates what our new web service will prepare for our internal workflow application to use. One field is a content field made up of HTML tables containing field labels and fields already generated. I prepared in Notepad++ for readability and then copied in, but it produced errors when trying to save (although generates fine)

<table class="form-content-table" width=100%><caption><h2 class="form-content-section-heading">Incident Details</h2></caption><tr><th class="form-content-label">Incident Type</th><td class="form-content-value">{__IncidentType}</td></tr><tr><th class="form-content-label">Incident Description</th><td class="form-content-value">{__IncidentDescription}</td></tr><tr><th class="form-content-label">Latitude</th><td class="form-content-value">{__latitude}</td></tr><tr><th class="form-content-label">Longitude</th><td class="form-content-value">{__longitude}</td></tr><tr><th class="form-content-label">Map</th><td class="form-content-value">{__MapLink}</td></tr></table><table class="form-content-table" width=100%><caption><h2 class="form-content-section-heading">Your Details</h2></caption><tr><th class="form-content-label">First name</th><td class="form-content-value">{__FirstName}</td></tr><tr><th class="form-content-label">Last name</th><td class="form-content-value">{__LastName}</td></tr><tr><th class="form-content-label">Email address</th><td class="form-content-value">{__EmailAddress}</td></tr><tr><th class="form-content-label">Postcode</th><td class="form-content-value">{__Postcode}</td></tr><tr><th class="form-content-label">Mobile Phone Number</th><td class="form-content-value">{__MobilePhone}</td></tr></table>

I minified the HTML down to about 1329 characters, but it throws an error on every save. I split in half (~667) but still got an error. If I split down to each row (also two rows), then it saves, and I can later concatenate them, but it might be helpful to (a) document what the limit is and (b) show validation error if template text entered is longer than max