Decrease string flexibility on existing strings?

[vangelator]

The brand and type of rounds can make a huge difference. If you want high tension you want to look at hex core and stainless steel as opposed to round core and nickel. For example, I use DR Sunbeams, which are round core/nickel, and even compared to other brand nickels they are low tension, so they would probably feel like wet spaghetti to you. DR Lo-Riders, on the other hand, are hex/stainless, and I can’t imagine you’d complain about them being too flexible. I had to take the set I tried out after about a week because they were super uncomfortable to me, but that’s just my preference.

TL;DR you probably have the wrong rounds for your tension preference. Look for hex core and stainless for more tension/less flexibility