When trying to ko a Wylern the best way would probably be to trap the Wylern in some kind of trap/cage then ko the wyvern with tranquillizar arrows or a long neck rifle with tranquillizar darts. Or try to have someone on a really fast argi with someone else riding so you can be shooting the wyvern while the other person jukes out the wyvern.
I got a level 150 lightning egg and I was so excited to hatch the egg...that when I went to put the egg down I accidentally ate it instead. :( ps4 users: R2 ISN'T GONNA DROP THE EGG YOU'RE GONNA EAT IT LIKE ANY OTHER EGG. REMEMBER THIS. LOGIC BEFORE EXCITMENT.