I'll chime in again with a strong and unflinching vote not to euthanize this perfectly healthy animal for multiple reasons. 1. It outwardly appears to be just fine and has a good appetite and has been shown by veterinary professionals to have no medical issues. 2. It is an incredibly rare snake in herpetoculture that does not have an established CBB population within the hobby globally.
To be blunt: More people have walked on the moon than successfully bred boeleni in captivity. Euthanizing a rare, adult, breedable, $10k-15k-20k animal because you are stressed about it losing a couple hundred grams at a weight of nearly 20lbs is absolutely absurd. Please relinquish this animal to a reputable keeper working with Boelen's if you are so insistent on having it medically extinguished. End of story. Period.