Usually I look for an edge about 0.5cm (1/4 inch) wide, unless they are very large (9cm or more) ravioli, in which case I'll allow 1 to 1.5cm.
However, if you're using egg roll wrappers, rather than fresh dough you made yourself, you might want to allow more generous margin than that, as you did. Therefore the ratio depends on both the type of noodle dough used, as well as the size of the ravioli.
Other things which make ravioli pop open are:
- not getting the edges wet or not pressing them enough
- air trapped in the ravioli
- filling or oil caught in the edge dough
- rough handling during or after cooking
- a filling which is too wet (uncooked spinach, for example)