OK, I put that code to the test, and it seems to work. In fact, I found an even better route to go. I altered the code a bit, and call the custom_post_template field and use the existing templates.
I put the following code in my single.php
<?php
$custom_post_template = get_post_meta($post->ID, 'custom_post_template', true);
if ($custom_post_template == 'TemplateA.php') {
include(TEMPLATEPATH . '/TemplateA.php'); }
elseif ($custom_post_template == 'TemplateB.php') {
include(TEMPLATEPATH . '/TemplateB.php'); }
else {
include(TEMPLATEPATH . '/single-default.php'); }
?>
It seems to work great when I deactivated the plugin. The best part is that if the plugin someday is updates, it is easy to switch back. You can also frontload the templates for your most common traffic to minimize the load a smidge. In my unscientific tests, this seemed to be a hair faster than the plugin.
Hope that helps someone.
Regards,
JT70