I know you’re a Sweetheart fan, Tim. It’s interesting to know that you favor the old design most. I tried one very early on, but was too new a whistler to judge its quality. Since then, I owned a Dymondwood Pro, which I liked a lot, but found to be a bit too loud and strident for my needs.
As it happens, I’m the one who jumped on this opportunity to grab a huge bunch of stuff at a rock-bottom price: https://forums.chiffandfipple.com/t/entire-whistle-collection-fs-sold/64245/1
This was a fantastic deal, and included a few real gems that I’ll hold onto. Among them was a like-new Sweetheart ‘Mello’ model, in permali laminate. I really, really like it. It has the look and feel of wood, is not ‘recorder-like’, and is rugged and low-maintenance. This alone was worth what I paid for the lot ---- but I’ve also got a gaggle of other fine whistles and new Yamaha tenor rec**der, to boot. …gotta start thinning the herd soon. 
Does the Mello model have the new style corking? The one where the cork is inside the headjoint and instead of wrapped around the tenon like a usual flute? That’s the part of the new models that I don’t care for. I had Ralph’s Resonance flute for six months and sold it because of that cork design. I understand why it’s supposed to be an improvement, but I just don’t like it.
You got a real bargain lot with your purchase though. Good on you!!
Yes, it has that internal cork. I think the idea is similar to Terry McGee’s ‘minimum disruption’ tenon: Minimum Disruption Tenon
Anyway, it works well enough. I like the sculpted mouthpiece on the ‘Mello’ model, and the gentler tone, (compared to my earlier Dymondwood Pro). I can mute it even further by putting an O-ring directly over the window, and it becomes a great practice whistle with no loss of intonation. Without the mute, it’s loud enough for a session, but not piercing. Very nicely done!
I was also pleasantly surprised by a few of the other things in the package: a nice Susato B, a Hoover white-top on a Gen Bb tube, a wonderful home-tweaked Feadog C, and an equally nice home-tweaked Gen D. And I also got that massive tenor recor**r. Holy smokes! 
Anyway, I’m a happy camper. 
I have a review of the Sweetheart Pro D on my website
www.tinwhistler.com, click “reviews” on the left
Thanks Tim for the suggestion about the cork joint. I never take the whistle apart. Since it’s so small, I’ll just keep it together so the cotton joint won’t wear out. But if it does, then I’ll send it to my friend in Boston that repairs wind instruments and have him put in a cork joint.
I don’t blame you for that. Even though many might consider it heresy, I never take mine apart except to clean and oil it about twice a year. Even with a cork joint, it has never leaked or failed in any way. The cotton only lasted a couple of months because in the beginning I was doing it the ‘right’ way by taking it apart all the time. But since then I’ve only replaced the cork twice in 20 years, and probably didn’t really have to do it the second time.
Oh, be sure to grease the cotton well, it seems to take a lot more grease than you’d think by looking at it. Hope you get many long years of joy out of it!
Yes, I agree that the internal cork/minimum disruption idea works; Ralph’s (actually Walt’s) design played very well. I didn’t like the fact that you couldn’t maintain the instrument yourself. I do all my own re-corking, but that design means that you have to send it back every time. According to Ralph, the cork has to be machined to fit the flute exactly. You can’t do it yourself and the majority of instrument repair guys in the average music store won’t have the equipment. That means that should anything happen to Sweetheart Flutes (God forbid) then we either have to find someone to do the work or we’ll all be out a lot of flutes and whistles. I just don’t trust that kind of scenario. I’ve bought my share of white elephants.
Thankfully, Ralph did say that you could re-cork it in the traditional fashion, but that defeats the minimum disruption concept.