Jpen-Cpen RPB (Jpen - Kpen RPB)

It is better to buy rubber and try it on your J-pen. It is less expensive than buying  a new set up.

If it is single ply hinoki, maybe it is not suitable because it is too thick and you might find it uncomfortable to hold.

GenomicsKnight,
How do you have your FH and BH rubber, do you have it up to the handle or do you leave some space for your fingers  ?

No, I don't do RPB, and I still have my J-pens (Cypress R, Speed 90/9mm). In fact now I will start to use my Kokutaku special 10 mm which is a squared J-pen. I find the wood soft, so I will use F1. And what brand is your blade ?

My goodness, you are a real collector of single ply hinoki. My compliments. If you intend to buy Kokutaku, then buy the 10 mm thick which is not available at the website of iruiru, but you can ask M/s Suzuki about its availability.

I used to use Darker J-speed 50 (8.5mm) double-sided round Jpen blade. It is only 65.4gm. If it's with the two japanese rubbers set up, 145 gm only. I shaved the one side of the cock handle. So, it is set up as Jpen but both sides don't have cock layer for the finger place. Now I got J-speed 90 Cpen (82 gm) but it is heavier than J-speed 50 Jpen.
PM to me if you're interested in.

It is absolutely possible to do RPH on J-pen.  I thought this is even more powerful than C-pen rph as the blade won't fly away on powerful PRH strokes.

I have now 4 such j-pen rackets apart from other C-pens for RPH.

BTY Tectonic with Bryce front and LKT ProXP rear
BTY HCK with LKT ProXP Front , RITC 729-2 German Sponge rear
Darker J-Speed 90 (8.5mm) with Donic Gallardo Power Sound front, Donic F2 rear
BTY Lendido with Magna front and RITC SuperFX rear.

Tried to use a normal and a lighter rubber, with faster one on front side, to balance out the weight or two normal weight rubbers will make the whole racket too heavy. Two light rubbers may make a racket too light.
I am going to have a Andro Plasma 470 on the front of Lendido and  possibly Innova Ultra Light on rear, to have more control and speed.
Except the HCK, I like the other three with good solid feels but the HCK blade is the lightest.
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The Darker J-Speed90 got no cork to sand on the blade surfaces and thus the most convenient to stick two rubbers.  THough, any j-blade will do but taking out the cork on rear surface.
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No objective measurement but just hand feel. It is light that I put a heavier than normal RTIC 729-2 on the rear side. Now, the weight and feel are comparable to the other three. Not a major issue as I am now mostly playing with Lendido and J-Speed 90.

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Reverse penhold Jpen- Kpen.