The answer is maybe. Some people report it works fine in tandem with other opioids, and others report that it doesn't. I've had it work synergistically with low doses of opium, but haven't tried other combinations.
Only way to know is to try it out. Definitely no need to worry about an overdose.
That was pretty much going to be my answer. If you want me to shoot from the hip, I'm going to say that I doubt the Kratom will help significantly. Fentanyl is in the upper leagues in regard to potency. Even with dosage being a relative thing, it's safe to say that if a Fentanyl patch isn't doing it, it's unlikely that a drug as mild in potency as Kratom isn't going to make the difference you're after. The time, expense and so on would probably be better invested in different options.
Kratom is a plant. Like how Opium is a substance containing several different active substances, mutually influencing each other, Kratom is a collection of Opioid alkaloids based around Mitragynine. We are avidly discussing this in another thread regarding the Morphine Milligram Equivalent of Kratom, but it's a difficult thing to do with accuracy as lay-people, over the medium of the internet.
But, based upon what I've heard and read about Kratom, I think a comparison could be made to Codeine on the low end and Hydrocodone on the High end. Highly potent strains of the plant might reach the potency of Oxycodone. What we mean by this is in the neighborhood of one gram of Kratom being equal to 5mg-10mg Hydrocodone for a decent, average potency specimen. This is all hypothetical, but I think it's close.
So, it could make a difference yes, but ,my most honest advice would be to look for a more potent Opioid than Kratom/Mitragynine. I don't ever advise people directly to increase their dependency on Opioids. I don't believe that would be right. However, if your mission is to start taking more Opioids, your current goals would likely be better fulfilled through stronger Opioids.
However, taking more Opioids rarely leads to a stable, chronic regimen that consistently relieves pain. I wish it did, but that's just not how these things typically go. If you're willing to increase the dose now, who's to say you won't keep increasing it? Only to make the decision here and now that you're not going to increase your Opioid intake is the guarantee that you won't suffer the consequences of a worse dependence. This is just my opinion. I'm not lecturing. I only want you to be at your best.