seal and send invites

Hi all:

I really like the simplicity of using seal and send invites but I wanted to get opinions from someone else who has used them....I have 2 major concerns;

1. I am worried that the response card will get lost in the mail as they are so thin. So if anyone has used them please tell me your experience.

2. will direction cards for the church and reception fit in there without falling out??

any input is very greatly appreciated, and I thank you in advance