dream boat

That's not true, the old boats for the most part run very slow and sloppy. Wet and a lot of rolling. A newish Sunseeker would run in 5' seas..... like the Manhatten 64'. Hatteras 64' MY (albeit wet) I crossed the gulfstream at 28 knots in 5's off the beam port corner of the bow. Viking SC's don't handle rough seas as well, they creak/groan and pound. I ran a 58' Viking SC express and in 3' seas I had to start backing it down.....a 2014 56' Fb princess was no better. Feretti's run pretty decent in a sloppy sea. A lot of the Custom SF's would eat up 5' seas pretty well in the 60ish' range.....Jim Smiths, Bayliss', Lightenings, and others. I came out of Government cut with 6's with occasional 8's in a 2004 54' Hatteras SF one time and lit it up to cruise and turned the corner and ran to Key west at 33 knots and the boat just ate it up and it was comfortable.

Add Riva to the list as well. A 56' Sportriva or better yet a 75' Venere. The 56 is a bit small for that but the 75 would handle it nicely. Actually the 63's do but they don't come in a bridge model.

Now, I'm going to say most would not run in those conditions at speed. Most owners operating their own boats won't tackle above 4' and some want less than that. They lack experience running in 5 and 6' and so they shy away from it, which means they never get that experience. Part of our training included those type conditions. When our training captain would see them, he saw an opportunity to teach us. It's not our preferred conditions but ultimately we'll all encounter it and better to have confidence in the boat and yourself than to find yourself unprepared.

Heavy DOES NOT equate to a good ride in rough seas. That is a myth more than anything. I can't stand the ride of OLD Bertrams or Hatteras or Viking Motoryachts in a rough sea (beam or stern) where they wallow around and roll from side to side. I'd rather not have to brace myself because I feel like I'm getting ejected out of the helm seat like on the old Bertrams and Hatteras in a beam sea. A hull is designed to carry a certain amount of weight, provide a certain amount of lift, and once past that, which most old builds did, the hull doesn't have the ability to perform like it's supposed to.

Take a look at SF. The good custom boats outride the best production boats 2 to 1 and they're half the weight. Ride quality is based upon momentum. The lighter the boat (within reason) the better it rides on the same hull. Now don't confuse light and flimsy as a basis of this. But light and strong is. Too heavy for the hull design and the hull just wallows from side to side in a beam sea and all over the place in a stern sea. I've had 58' Searay's out in 6' seas and honestly it didn't ride too bad in it and that was in Lake Erie 6'. Wet, pounded a little, but was stable and still about to maintain 20 knots.

Some of the new motoryachts ride better than any of the old boats. I took a new 74' Manhattan on a 50 NM run and did it all at 26 knots in 5-6' seas both off of the beam and dead on the bow. It didn't wallow, it didn't roll, it didn't pound. It just ate it up and there was not one ounce of spray over the rubrail. The European MY's tend to ride better than the US ones.......Most of them never have stabilizers installed because they're simply not needed. The 1988 75' Hatteras MY I used to run a lot, would have been not fun at all with 5-6' on the beam.

That's probably one of the greatest feelings in the world J, haulin' butt in good sized seas and chewin' them up like they weren't there. It put's a smile on my face every time, that doesn't go away for a few days. (Can it Ralph....we all know what a sick, twisted individual you are!)

J, there's a few Jim Smith's for under a million between 89' and 96'. I doubt Ralph's client would want something that old.

Some of the quality European builders are capable of doing the job your client wants. Try a UNIESSE 58 MY.
As long as you can put up with a total lack of warranty support and some strange plumbing ideas they are a good quality, good sea boat builder.

How would a 70' - 80' leopard or mangusta handle in 5' at speed?

Mangustas handle horribly. A friend of mine runs an 86', they don't travel in anything more than 3' because the boat pounds so badly. Yes 3'.

Well pounding wouldn't surprise me at all on the 72 and 80 which are their two surface drive boats. Pershing, with Arneson drives, tends to pound a bit as well.

Surface drives do not make a boat pound. Magnums run very well in a sea. Having too flat of a bottom and not sharp enough of an entry because you're trying to maximize speed and don't know of better ways to do it, are.

Didn't say they did, but both surface drive boats mentioned are built for speed versus ride so doesn't surprise me they have very similar ride characteristics. They target the same audience, have similar performance. Having seen Mangusta and ridden in a Pershing then, the ride of the Mangusta pounding was no surprise. Similar boats, similar rides.