Welcome back to the madness....you have come to a good place here.
I'll save you some time here,
Uncle Nick's Powder Baffle Templates
I was going to post up you should look for that as it has about every sized one you could ever need on it. You just print it, cut out the one you need then tape it onto some thin sheet metal and cut them out.
Back to the Uniflow, I also use them and have 4 or 5 of them. I use a couple for rifles and a couple for handguns depending on what I am loading. One is mounted on my progressive and stays there, the others well they are moved from one stand to another when or where needed. Since I also work up loads at the range I have a plate that is screwed to the base I mount the press on which I screw one into when I go there.
Those reference marks as mentioned are just that reference marks. What I do when I head to the range is to weigh out the minimum to maximum charge weights using those to just down in my notes as to what number of turns gives me what amount of powder. Just as an example, say I using IMR-3031 and the start load is 35grs which comes up to the number 3 on the stem, but also takes 2 more full turns or say 2 full turns plus 3/4 of a turn. I would jot that down as 3+2 or 3+2.75. I do the same for the max charge weight as well. These are all weighed out on a scale while i am at the house and verified using several dumps to check each end. Then while I am at the range I can reference my notes and be very close to those loads without having to have my scale sitting there in the wind.
For handgun loads I work them up using the scale only, weighing out the powder charges individually. Once I know what each final load is, I will make a note for that mark plus how many turns it takes to hit that weight. Just like with the rifle loads only when i set back up to load the same load at a later date I will again weigh it out to verify that charge.
There is simply too much of a chance with faster powders to get in trouble especially if your playing with different bullets which might seat deeper in the cases and give you pressure spikes. Comparing most handgun powder to rifle powder is like putting up lump coal against flash powder. So you want to be a bit more exact on the smaller amounts of faster powder. Just follow a procedure, always use good current data that you yourself have verified through the powder or bullet manufacturer or an up to date manual and you will be fine. While there are some decent video's out there in cyberland, the best info comes from the main source of the components your using. There might be a hundred different recommendations posted up here if you asked, and MOST would be good, but it only takes one to ruin your day.