I was a huge cramper!!!! Big Time pain in the inner thighs after and during hard efforts. A couple of years ago that could be 25 or 30 miles into a training ride. As my conditioning increased my cramping subsided.
I'm a huge believer in that if you've addressed the electrolyte situation and are hydrating well, then conditioning is your key and there's no shortcuts here. Just get good recovery and use harder more intense but shorter efforts to adapt your body for the longer efforts.
If you are a salty sweater you can ad a bit more salt to your drink while riding. I use a pinch of mortons lite salt in my accelerade.
I use a calcium supp. called Sportlegs (3 caps pre-ride) I firmly believe these have helped as I seem to cramp more on rides that i forget to take them.
Conditioning, conditioning conditioning(and sportlegs)
I'll eat my hat i I'm wrong!
Good luck