Best way to make bubble flares on 5/16" NiCopp tubing?

Need to make bubble flares on 5/16" fuel line.

Got the rental tool from O'reilly's and can get something that will probably work but it's more like a fluted end than a bubble, and they seem to want to come out a few degrees off square.

I have the Titan hand tool for 3/16" brake line and it will do a nice bubble on that size.

Summit has a version that does multiple sizes including 5/16", but it's like $160.

Long ago (probably close to 15 yrs ago now?), I replaced all the brake lines on my truck with NiCopp (Cunifer) tubing and fittings from Fed Hill.  Back then, they had a program where you could rent their very nice flaring tool with the appropriate die set for whatever line you were using.  They'd also send you a tray full of fittings for that size line.  You'd use whatever fittings you needed, send the tray back along with the tool, and they'd count up whatever fittings you used and only charge you for them.  It was incredibly helpful, and the tool worked spectacularly.  I must have flared 30-40 ends, and when I put it all back together I didn't have a single leak.

Not sure if they still do the rental thing, but worth an email to them.  FYI, their website has not changed since I did that work!

Here's some pics of what I have been able to do with the O'reilly's rental tool:

Flare on 5/16" line - ok, but not really a bubble, and a little lopsided:

This is what I was able to do with the handheld 3/16" tool if I skip the first step and just partially torque against the 2nd step Die:

Wonder if you could use a swage lock instead, might be an option if Tool is hard to find. 

buy fancy one off amazon prime, use one day, box back up.  Return?!?!?!?!

Sooo...I realized I am not correctly using the term. I don't need an actual bubble flare. I need a flare to help keep a rubber hose in place like this:

I haven't found anything really online as far as tools or youtube instructions on how to accomplish this.

I also have come to the conclusion that I am overthinking it, and will just do a few more practice pieces and decide on my technique and make my flares with the tool I have. My only real concern is the difficulty getting the rubber hose over the "square face" of the test flares I have done so far.

Trying to avoid having fuel lines that are really hard to service when I am laying under the car with gas dripping in my eyes . Many of these connections are in tight quarters around the rear axle.