I have pretty much every single wetsuit part accessory ever made and tried them all in our cold winters (I kite down to 0c, 10c I'm usually in boardies or my shorty) and I have pretty much the same recommendation for you that I give to everyone else, buy a neoprene jacket, like the Hyperflex Playa. The point of the jacket in my case is I will layer it over my 4/3 go do down to 0c but in your case I believe a hyperflex playa over a shorty or that longjohn will be perfect. It gives you the effect of somewhere around 1 or 2mm extra warmth. If you are in heavy waves it probably isn't an option to ride out there with it as water can get caught in the jacket but for everything else it's great. A lot of times you don't actually need the full wetsuit, all you need is a little extra warmth when you are on the beach, and the jacket is perfect for that, it keeps your core warm when you are just standing around.
As for the shirt I recommend against it. The problem with a neoprene shirt (at least for me) is it's difficult to layer with a shorty because you end up getting constricted so much. The jacket is loose so you can layer it with anything but the neoprene shirt is tight, so when you have a regular wetsuit on and the neoprene jacket on underneath it or over it you get too much pressure and as you know when you have bad circulation to your extremities it's worse than having the layer on at all. So I really don't like layering neoprene over neoprene, it really gets too tight and I also don't like how it wears you out fighting against the double neoprene layer.
To add to the jacket idea, you want to be able to go out in your shorty and then just add accessories, so make sure you have neoprene socks, boots, gloves, full hood, spring hood, and then you add that to your neoprene jacket you can just get into your shorty and then add additional layers and accessories as desired to warm up. Another item I have that I really like is the hyperflex "first layer" it's a layer that goes under your wetsuit so you can wear say a 2mm long suit instead of a 4/3 and with the hyperflex first layer it gives you a little bit extra warmth and it makes it much easier to get into your wetsuit because it's like you have a body sock on. If you are not riding with a hat yet, that actually is the first item you have to get. I know hats don't look cool but any kind of neoprene beanie, full hood, anything like that will add the effect of maybe an additional 1 or 2mm to your suit. Of course you don't really make it easier to go kiting when you add all these accessories, instead of heaving and tugging on a fat wetsuit you are putting on one accessory after another.
Anyway that's my general feeling about wetsuits, buy as many accessories as possible, it lets you go colder with a lighter wetsuit.
I have never used a longjohn with a neoprene shirt I have always used that shirt with a shorty, and didn't like it but maybe with a longjohn it will shine, try it see how it goes. But I would probably go with the hyperflex playa before anything, as it is the most versatile neoprene piece of clothing I have and unlike other neoprene it doesn't really wear out because the fit is so loose it doesn't rub and wear like your other neoprene does, so that playa jacket will be with you for a decade.
If you like the combination of shirt + longjohn let us know how good it is! If it works good I'm definitely adding a longjohn to my big collection of neoprene clothing, since I already have that shirt which is doing nothing for me.
Last edited by edt
on Wed Jan 25, 2017 8:03 pm, edited 2 times in total.