Well, without error messages I have no idea what your real problem is. I do have some suspicions though, which I have detailed below. Next time you post something like this, include the errors you are getting (no matter how large) it will go a long way in helping us help you solve your problem.

package MyApp::Schema::Result::Item;
use Moose;
extends 'DBIx::Class::Core';
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You have already been told that this approach is not advised, you should be using DBIx::Class as it was intended.

package MyApp::Model::MD;
use Moose;
use base 'Catalyst::Model::DBIC::Schema';
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This doesn't make much sense here because you are using Moose then using base. I think what you really want here is:

package MyApp::Model::MD;
use Moose;
BEGIN { extends 'Catalyst::Model::DBIC::Schema' };
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This is exactly the code I am using in my catalyst apps right now. If this still doesn't work, then I suspect it is because of how you are (ab)using DBIx::Class in MyApp::Schema::Result::Item and you should change that.

package MyApp::Controller::Item;
use Moose;
use base qw/Catalyst::Controller::FormBuilder/;
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Again you have this mix of Moose and base, what you really want here is:

package MyApp::Controller::Item;
use Moose;
BEGIN { extends qw/Catalyst::Controller::FormBuilder/ };
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