A rotary that is hopping around - buffer hop: this is generally the result of too much or too little product on the pad. If you tilt the rotary off to an angle as well, I find that it can also hop about and tug at you.
I have no experience of the Hitatchi rotary, I use a Makita myself, and if I flow with the motion of the rotary, ie dont fight it but flow in up and down motions with the machine and ensure I dont overload the pads with product then I find the rotary works very smoothly... Also, keep a check as you work that pads are not becoming lcotted with product as this will act to cause buffer hop. Keep a toothbrush with you for remvong clotting from the pad, or better still switch to a clean pad. I will use two or three pads per car for one product to ensure I always have a clean and unclotted pad throughout - saves times with the toothbrush.
I use
Meguiars pads with the Makita (Wx006 pads) and find them excellent, and have had no control issues with them unless the pads have become overloaded with product. Also, what speeds are you polishing at? I prefer to polish at lower rpms - with
Menzerna I go no higher than 1500rpm, with
Meguiars no higher than 2000rpm and only very rarely would I use the 2k speed. I find product less inclined to dry out a lower speeds. Also for finishng, with finishing polishes such as Menzerna PO85RD I will polish at 900rpm followed by a final pass at 600rpm - very slow, but gets a crystal clear hologram free finish that beats the finish from the PC hands down and also the slow speeds don't dry out the product.