It seems easier for me to update the
Ti-khana Venomwing Pterosaur to show how I'd do it.
Okay, checking the CR Calculator my
Venomwing Working Draft has a wee problem.
Its
Magic Resistance with AC 14 and 5 hp gives the Venomwing a Defensive CR of 1/8.
However, +5 to hit means the Venomwing's Damage Per Round must be 3 or less for it to be
Challenge 1/8. Any higher pushes its Offensive CR into 1/2 and exceeds that limit.
There's basically three solutions:
Solution #1: Keep it as it is and have it do piddling damage. i.e. a Bite doing 1 piercing plus 2 (1d4) poison.
Solution #2: Drop DEX to 15 to make it +4 to hit (we can keep it AC 14 if you like), which allows the DPR to increase to 5. i.e. a Bite doing 1 (1d4–1) piercing plus 3 (1d6) poison.
Solution #3: Boost it to CR 1/4. Maybe STR 6 (–2) with its DEX 17, and a +5 to hit Bite doing 1 (1d4–1) piercing plus 3 (1d6) poison. CR 1/4 would also let us squeeze in another Hit Dice for Hit Points 7 (3d4) if we want to make it slightly tougher.
I'd go for
#3 or possibly
#2, which do you prefer?