fastest used flatwater ski on a budget

What family of boats would be considered to be among the fastest on flat water for long distances? I weigh 220 pounds, so that excludes some (Think, Stellar SES). Since this would be my 5th ski, I cannot consider brand new ski's (too expensive). This boat would be for flatwater only; no ocean. I don't mind unstable ski's, in fact getting used to an unstable boat on flat water may do me good for surfing/downwind on my XT, 2good Chalupski, or spec. I used to have a Huki S1-X before it broke and had no balance problems on it.
This is what I have in mind to look for:

Millenium, Custom Kayaks Icon, V10, V10L, S1-X, Fenn Elite, Mako 6, Twogood Mako Pro, Stellar Elite SE or SEL, Nelo Oceanski XXL. The first two seem to be cheapest ($700-$900 carbon), while the others sometimes come up for ~$1500 or so for carbon, ~$900 glass.

Are any of these obviously faster or slower than the others?
Am I missing any boats that could potentially be bought second hand in the price neighborhoods listed above that are just as fast or faster?
I assume I have to look in the ~21' x ~17" class only. I assume these are much faster than 19' ski's.
I assume carbon is slightly faster, but not much on long distances.
I thought about K-1's as I hear they are faster and more unstable than surf ski's, but not sure about open cockpit and aren't they only 17'? how can they be faster than 21' ski's?
thanks

I had a short go on a glass Mill on bumpy water, and it felt very fast. Probably as fast as my E-V12. But feelings are subjective. I did not like the non-adjustable double foot wells. It was a tad more unstable than my E-V12, but not terribly unstable. Nelo's are said to be very fast. The K-1's can be faster in short distances, but only by one proficient enough to keep it upright.

Whenever someone asks me what ski to use for flatwater, I chuckle a bit. Surfskis, even the more aggressive ones like the nelo and atom, offer no appreciable advantage for flatwater at all over an intermediate or elite k-1, except that they might be more "versatile". But you already have four skis right?, You don't need versatility. I would be looking to add to my skillset and paddling proficiency by paddling a k1 you can really drive, not by buying another, marginally faster, ski. If you are up to the challenge, a k1 will expose all of your "skeletons in the technique closet" and make you a better paddler without question. I think it's possible for many ski paddlers to make a quantum leap in stroke technique by spending some time in a sprint boat. (although it won't help your downwind skills much) BTW skis and olympic boats are about the same insofar as their ostensible hull speed is concerned; the difference being in a k1 hull speed is a very soft threshold that can easily be surpassed by skilled/fit racers. Once you really learn to drive a k1, you will understand that all surfski's are a compromise craft best suited to chasing downwind and not racing against real flatwater kayaks, unless you are into the ultramarathon, Carter Johnson kind of thing. Its true that some skis are markedly faster on the flat, but honestly that owes as much to more agressive posture/ergonomics than anything else. If you are just cruising around the pond in a ski it had better be your only boat or it's just plain silly IMHO.

MikeyA, the speed of the boat in flat water pretty much comes down to the wetted area of the hull.

A cylindrical shape has the least wetted area for the same displacement than any other shape, it also offers nothing in the way of stability.

Any deviation from the cylinder (with pointy ends)that adds stability will slow it down in terms of drag.

So yes a shorter craft can be faster.
It simply has less wetted area, but you pay for it in having something that balances on a knife edge.

This is a very good article on the basics.

Closeted skeletons aside, if we're just cruising 'round the pond why go for the marginally faster k-1 when you can make a k-4 look like a human powered barge:

I've seen the earlier footage on these but never saw a speed measurement before.
Man that's fast!

So is a K4 it seems.

I wonder if it would work in the waves.....