For concealed carry, I would leave it as is. If you are confident, and always mindful, and therefore don't really feel it will fall out, I would say it will work just fine. Millions of people carry concealed daily in non retention holsters. If you think the velcro strap would help, I would also suggest you try that. It would be easy to remove if you don't like it.
For open carry, I strongly suggest you get a Serpa or a Safariland.