Epic V8 Double, V10 Double or Fenn XTS Double?

My club thinks about buying a double surfski. The idea is to put two weaker paddlers in a double so they can keep up with the faster paddlers. I am thinking about Epic V8 Double, V10 Double or Fenn XTS Double. I guess the V8 will be at bit too slow. Waves are not too big. Wind bft 4 on a 800m wide river. 

Could You expand a bit on this: "The idea is to put two weaker paddlers in a double so they can keep up with the faster paddlers." What is the approx. speed of the faster paddlers and what are the speeds of the slower paddlers?

faster ones 10km/h, weaker 8-9 

In that case I would go for the lightest V10 Double I could afford.

My plan is to buy a Nelo 600 Double in the spring. By no means it seems a fast boat on flat water, but I wanna use it for surfing with beginners.

If I were searching for something I could use with proficient paddlers on flattish water, I would only consider narrow boats. F.e. this one:  webshop.aterra.se/surfski/ss2-dubbelsurf...ology-blast-ss2.html  

I am unsure if the boot is stable enough. Our girls have been happy with V10 and swordfish in calm conditions but not when it is windy.

I have a V8 Double and a V10 Double (both Ultra).  For two average skilled paddlers, the V10 is a handful and takes some time and dedication to get comfortable with.  If one of the paddlers has less than average skills the experience can be quite challenging.  The V8 is much more forgiving and probably faster if only paddled irregularly.

People with shorter legs and more compact frames may find the V8 Double more comfortable.  I can just barely reach the pedals of the V10 Double and find the cockpit large.  No such issues with the V8. 

I own a v10 double and have used the v8 double. I would go with the v8 double if you are deciding between those two boats. The v10double is only faster with skilled and strong paddlers. The main issue is stability. I consider myself advanced - I paddle elite skis comfortably in all conditions. If I am with another advanced paddler we are amazingly fast in the v10 double, at least on the flat. With an intermediate paddler in the back it is a mixed bag. If they are lighter than me it goes ok. If they are heavier than me the boat is wobbly and much of the speed advantage of a double is lost. With a beginner in the back, It goes fine if that other paddler is a petite woman who is too light to throw off the balance much. But with a beginner in back who is my weight or heavier it is utterly horrible.   The boat wobbles violently, and the only thing keeping it upright is my own core strength and balance. It is a slow, frustrating, joyless experience that leaves my shoulders and back sore for many days. 

As far as speed, the v10 double is 0.5 - 0.7 mph faster than a single elite ski assuming there are two equivalent paddlers in it with no balance issues. The v8 double is the same speed or perhaps 0.1 - 0.2 mph faster than an elite ski, assuming equal and highly skilled paddlers in all craft. 

Two beginners in the v10 will be swimming a lot. Two intermediates in the v10 might do ok if they have great balance, but will probably be slower and having less fun than they would be in a v8 double where they could lay down power. 

Thanks a lot for all the information. I am sure the V10 is not the right boat. Now it's just a question of the Fenn or the V8. Nelo is although available but that  boat is really wide. 

On open water I race Stellar SR whilst my wife races a Carbonology Vault; on flatwater I race a Stellar SEL and she an ICF K1. After looking at the various Doubles, we bought a Carbon Vacuum Fenn XTS. This is primarily used for FUN paddling plus taking friends and family out. Towards the end of 2018 we decided to race it in a Club flatwater race, just to see how it went. In these races (11.5Km) my wife and I do very similar times in our singles and were quite surprised that we were about 5 - 7% quicker in the XTS. We have since raced it a couple more times, with similar results. Yet in the "rough stuff" this ski is really in its element; stable, comparatively dry, yet goes quite quickly. I am very happy with the Double XTS as a great all round boat and would recommend it highly.

I own a Fenn Elite S Double, and quite a few of our club members have XTS Doubles. The XTS is an amazingly quick, stable ski and punches well above its weight in terms of performance. In flat conditions it is only slightly slower than the Elitre S, but in windy conditions, especially big downwinds, it is easily as quick as my Elite S. Go for the XTS Double, you won't be sorry, it's a great ski!