First boat for tall new sailor with dodgy bacK

Hi all, sorry for yet another new boat post...I am completely new to sailing and have just enjoyed doing the level 1 course. Whilst waiting to do the level 2 course next month I am pondering which dinghy to purchase. I am 6’3” and about 70 odd kg, in my late 40’s with a dodgy lower back and knees which grumble after too much kneeling. On this basis I probably shouldn’t be considering a dinghy at all but life is too short and I can’t afford a Bavaria yacht...
I am looking for something which is able to move along nicely but is also comfortable. I think comfort will equate to a high boom and a deep cockpit where my feet are lower than my bum. Also not too heavy for pulling up the slipway. (Pulling a Pico was fine at around 60kg.)
At present I’ve only sailed the Pico which has quite a high boom but not much height between feet and bum when perched on the side decks and felt very cramped.

I was told at the level 1 course that a number of taller sailors at the club sail the Supernova. Is the Supernova likely to be more comfortable, ie have a deeper cockpit and similar or higher boom? (I’m sure its a much better performer but need to make sure it’s comfortable). I originally wondered about a Solo but it was mentioned that the boom is very low and the cockpit isn’t particularly deep. Images of the Solution suggest it has a deep cockpit and reasonable boom height but there doesn’t seem to be any used ones for sail. A shame as it’s a light boat too.

Can anyone recommend any other boats that maybe suitable for my situation? As a total beginner I’ll need something straightforward to sail and which doesn’t break the bank for a first purchase. The club sails on a large reservoir and I think races Solo’s and Aero’s and has a handful of Supernovas amongst other dinghies. Difficult to get close to other folks boats at this time with the Covid situation so I’d be grateful for any guidance anyone can offer.
Many thanks,

Based on the knees and the fact they sail them at your club Solo. It has a proper thwart to sit on downwind and in the light stuff. Whatever boat anyone tells you watch some YouTube videos of people sailing them and look out for kneeling, also at you club if the people from one class are wearing knee pads. 

Thanks for the replies guys.
Looking again at the Solo I have to say it does look comfortable. It’s a big boat though, heavier to pull up the slipway and I would imagine a handful to right after a capsize? Hopefully I won’t capsize quite as often as during the windy conditions I had on the level 1 course but it has brought this aspect of a boat selection to the front of my mind.
The other option I suppose is to go for a training type dinghy such as the Hartley H12 perhaps? Lighter and hopefully comfortable, but with a smaller sail presumably making this is a slower less fun sail?
As you have said I’ll need to try and find a way to test some of these when I’ve got the level 2 out of way...
Thanks again

Deciding to stay ashore when its windy is not a problem till you get used to the boat. Get your Class boat

With a training boat once you get things sorted- you really have to buy again.

Careful is good- but you will get going quickly- and with whichever class you choose a member of your club with the same boat is likely to help

Don’t discount something like a Vareo, high boom, deep cockpit. Solo is a great little boat, but isn’t actually that roomy.