Based on my personal experience with BGs in the 250+ range, I find my biggest error is under-correcting due to increased insulin resistance of the high. Have you noticed in yourself that your insulin sensitivity factor or ISF is more aggressive at higher highs than lower highs? In this context an ISF of 1:25 is more aggressive than an ISF of 1:50, an inverse relationship.
If you do find that it takes more correction insulin at the higher highs than the lower highs then go ahead and use it. I believe that splitting the correction will almost always prolong your hyperglycemia. There are exceptions, of course, and you need to be aware what your personal exceptions are with any rule of thumb.
Insulin is a powerful tool and you are right to respect its potency. On the other hand do not be overly afraid of its power. Just ensure that you pay attention (set a phone alarm, if needed) and keep glucose tablets or other emergency glucose handy. Rapid acting analog insulins enter their peak glucose lowering phase about 90-120 minutes after you take it. This is a good time to review the effects of your correction.
I’m unsure whether you use a pump or not. I do caution not to use a pump if your BG is 300 (16.7) or higher. If your infusion set or site is failing then your correction insulin does not get delivered 100% and can lead you down the road to DKA. Without exception, I deliver correction boluses that target 300+ (16.7+) BGs with a syringe.
Also, if I doubt the quality of an infusion set/site and my BGs are very high, I just swap out my set even before I can confidently conclude that the set or site is the problem. If in doubt, swap it out!