Thank you for providing a photo of your Malibu and power chair carrier.
Use of ANY type of trailer hitch adapter/extender, such as the Brophy # HT5R that you referenced, will have an undesirable side-effect: it will reduce your hitch's tongue weight capacity by 50-percent. It will also introduce additional random motion of whatever is attached to the hitch.
Since your combined power chair and carrier weight is 266-lbs, this means that your hitch would have to be rated for over 500-lbs... view full answer...