Not sure if you're still interested, but I've checked two of my Munchlax trees using the following seeds and I've always gotten Heracross:
Initial Seed-Frame - Shake value, Species
B4040260-187 - 2, Heracross
D20E026C-14 - 2, Heracross
D90E0266-189 - 2, Cherubi
B80E0262-188 - 2, Heracross
The Cherubi was expected since I advanced an extra frame, but Heracross throroughly confuses me. When I attempt to slather any other tree with the first /656 being 0, the honey doesn't stick, and that's expected. Every other attempt of getting Heracross on a non-Munchlax tree has resulted in an Aipom, and I haven't managed to match up shake values and species at all with researcher. I'm thinking about giving up on this :(