I just picked up a new Saeco 640 DC (370gr, 40 cal) mold from the LGS and never realized that all of my dozens of molds are all Single cavities. So I do not own a set of magnum handles. My plans are to get a couple of KAL molds once I make contact (I still have not gotten a reply from them) and Accurate molds. 

So what are the best options? I know of the clamp type from BACO and Lee 6 cavity handles but am wondering if any of the makers have better choices (or if someone has a DIY design that is the Bee's Knees).

Thank you for your continued advice and patience,
Charles

In my own opinion if they the handles are not extremely comfortable to us.
Try modifying what you have until the actually do.

KAL handles are great, but I don't think they'll handle the double cavity blocks.
Might try a set of the locking mold handles they sell on Shiloh's web page.

I have Hoch (Saeco?)
Jones
Saeco
RCBS
Lee
CabinTree (original and MVA aluminum)
Hensley and Gibbs
Lyman
Of course the most comfortable to use are the old Lymans. They feel good in the hand and don't put the mold so far out that it feels unbalanced. The newer Lymans come next but are not as comfortable. The Lees are good but not every mold fits. The RCBS and Saeco are similar but, again, not every mold fits. The H&G is a 6 gang so out of the discussion. If the arms of the handles are a loose fit in the mold slot they can be fussy in realigning the mold halves on closing. The Cabin Trees can be unhandy because of their length but they do ensure a standard mold closing. The aluminum ones are less tiring in use. I like the Cabin Tree on my heavier match bullet twin cavity molds.

Why not just get Saeco handles for their molds? In my opinion the Saeco handles I own are some of the finest made. They're longer than most others, so it takes less grip strength too keep them tightly closed. Not cheap, but worth the extra cost.

These are Hoch handles that I modified for my own use. 
I drilled and tapped it for the four adjustment screws that are being shown.
These are used to perfectly align each of the mould halves on closing.
They also eliminate any swiveling effects and miss alignment of the alignment pins. 
They are also very well balanced and extremely comfortable to use. 
They can also be used for a wide variety of different moulds. 

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I have a friend who has several of those locking handles.
The blocks are so extremely sloppy on when mounted on them in regards to easily being re-aligned on closing the moulds have quickly been destroyed. 
Closed is actually completely closed and it easily done by hand and there is absolutely no need for what I would consider to be Vise Grip handles.

Well I decided to stop in at Trackofthewolf and picked up 4 of the Lee handles to start with. At some point I will most likely try the Aluminum lockers. Almost cost me more for the Lee's since the local constabulary decided to pull me over ( the one time I actually drove like an older responsible driver). He must of seen something suspicious about the car because he said I was stopped because it was drizzling and I did not have my headlights on. Anyway, he let me go without a warning. And thy showed that they were out of 56-50 Spencer brass but they actually had a few so I picked up ten to see if they will easily make 50 Remington pistol since I only have 20 pcs. of the BR&C brass.