I would warm the mold, take a cotton swab and cooking oil and lube the tails, inject holding some pressure for a bit and see how it goes before I did any mold modifications.
That is how I get my baby brush hog and twin tail grub molds to shoot.
I hand pour with a 2 piece aluminum. I use silicone cups and 1” copper tubes as spru extenders.
The copper tubes are cheap from hdw store. You might give them a try. They have solved some problems for me. Maybe they would for you.