Since when is the Doria 300ft deep? This is at 245ft in Lake Superior on the SS Kamloops, vastly colder (2-3C) but only what I would consider a modest wind driven surface current sometimes. She is a big ship but scooters are uncommon because she is laying on a steep slope and going up and down that fast on a CCR isn't especially pleasant, you have a much greater risk of things freezing zooming around (esp if you're on OC or BO), and you'll freeze without any kicking at all.
With 20-28mins of BT at an average in the 190-255ft range, this is a 2x 80s with an O2 bottle hung from the boat kind of dive for me. I could carry an al40 on the left under that al80, but keep the exposures modest enough to avoid the necessity of swimming around with it the whole time honestly - this is vacation and a 3 bottle dive is a bigger hassle for no value here. Net, runtime is around 85-100mins, about the longest exposure that's reasonable. You don't want to be stuck on deco as the boat is ripped from the mooring in a thunderstorm.
In these pictures, I have 2x 3L CCR bottles, an al13 of air as suit gas (it says argon but the boat didn't have argon), then 15/55 in the left BO, 50% in the right. Plus quite a bit of lead in a CF200 with weezle extreme+ underneath it. There is a long hose on the 15/55, but the 50% only has a 40" reg hose on it. My buddy taking the pictures had similar BO gasses and volumes.
