I wouldn't say that the size of envelope you use affects the chance of a reply.

I use the half A4 sized envelopes or smaller, but this is just personal preference.

I think it is more expensive to mail larger (an therefore heavier) envelopes, but if you have used IRC's you should have as good a chance as anyone else!

Hi,
I sent off autographs to 3 different celebs. I sent to all of them an almost A4 size padded envelope (SASE) with 3 or more ICRS. One celeb I have seen about 5 sucess on here all of which requests were sent AFTER I sent my request, another celeb someone who again sent their request after me got a reply back and they live in the state next to me and the autographs are autopen so there is no waite on actual celebs presence. The others is too early to tell. I'm a bit worried that I either didn't send enough ICRS to accomidate for the envelope being padded or that the celebs are not opening the mail because the package size is too large.

So I guess my question is is there a likelyhood I am not getting replies because of the type of envelope I have sent or could there be another reason I have not yet had replies?