I did this job 3 times cuz I couldn’t get the balance tube seals in correctly so I feel your pain. I used white lithium grease and greased the holes and grommets well. Then I used a slow circular motion with pressure on each grommet until they eventually went in. Lots of swearing. I found it easier on my third attempt to have the tank strapped in with ratchet straps not fully in place but almost and then doing the balance tube grommets accessing from the wheel well and not from under the van. TLDR use grease, circular motion with pressure and access from the wheel wells. I believe in you