What is the proper way to choose an appropriate AuxChain ID to merge mine with Dogecoin?

[david2278]

Pepecoin, a Dogecoin fork, is planning to do a hard fork which will enable merged mining with Dogecoin. Since there is a distinct lack of merged mining pools on GitHub, standing up a pool in a local development environment to merge mine on testnets is challenging.

Since we are unable to test, we have concerns of compatibility with Dogecoin, particularly with index collisions in the parent chain's merkle tree. We have tested for collisions by looping through the code in auxpow.cpp with all possible auxchain id's, heights (h), and nNonces (we set the nNonce to 0 as it seems the nonce will clash for "all possible nonces" according to the Merged Mining Specification). We noticed we get less collisions as the value of h increases. This seems to be the case with Dogecoin's AuxPow chain ID as well. To sum up, we have tested CAuxPow::getExpectedIndex with various inputs to test for the same return value (i.e. collisions).

To generalize, when choosing an AuxPow Chain ID to merge mine with Dogecoin (and other scrypt coins), what steps can be taken to prevent leaf node collisions in the parent chain's merkle tree and to achieve greater confidence of compatibility when merge mining with other auxiliary chains including Dogecoin?