Jenn - I started by taking my dog Jerri (75 # female shepherd) for a fast taxi - no prob. Then we went for a 3' flight down the runway and landed - no prob. - went home - next day we flew.
But she had on a harness with a leash (not from her neck but harness) and clipped to a D ring in the cargo floor - if we stopped fast she would not have hit the panel.
Jerri laid on a ski life vest as a pad.
Then I started flying German Shepherds for a rescue - pull up grab strange huge dogs - throw them in the back and go - and I never had a problem - IMC and all... Maybe just lucky - maybe just the breed.
I got tons of stories - going NORDO IMC and the dog knew something was not right and she stood up sat next to me and just put her head next to mine - I gave her a hug and we finished the flight - they are the best co-pilots...
I got another Apache (90# male) should have called him Aztec as his nose is more like that
same thing though - would fly the H3LL and not bat an eye.