I have a similar problem with my Miramar but perhaps not as severe. I have found filling the toilet bowl with water before I begin my "business" has pretty much "eliminated" the problem. Putting more water down after you flush just doesn't move the pile.
It's really not about the type of TP you use or the chemicals or dish washing detergent. All of those things will help when emptying the tank but have nothing to due with the cone that can build up below the hole. It is all about having enough water go done at the same time.
All of this said, I am unable or unwilling to have this conversation with all the users (especially grandkids and visitors). So I keep a 6' walking stick in the corner beside the toilet. If all else fails I have found that works wonders at eliminating the cone of "stuff". I simply wipe it off with TP when removing it from the bowl hole...job done.
I will say I don't have to do that at all when it's just my wife and me using the toilet. I do add dishwashing detergent, proper chemicals and use septic safe (quick dissolve) TP just to aid with the dumping of the black tank.
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