Why not use the incredibly cost efficient and well designed Neutrik connectors?
That kind of connector would be perfect for the D1 cables, they are meant to offer maximum value for the money. It wouldn't be a big deal to buy several reasonably priced XLR connectors from Neutrik, Vampire and Furutech and see what works best. The higher end cables I make are meant to offer maximum performance without as much emphasis on keeping cost down. That means I would need to purchase and test out the options to make sure I am using the best connectors I can. That is what would get expensive, plus the fact I'd need a balanced system to test them on. The middle of the line Furutech XLRs are about $325/set, Xhadow (high end vampire) are $260, Neotech are way up there too. A high end XLR cable is going to cost more than a single ended IC and it would cost me well over $1k just to research the options.
In any case, connectors are a big deal... there's often major differences in sound quality between RCA plugs. The Furutech FP-101 RCA plugs I use on my single ended ICs are over 4x the price vs the FP-126s on the D1 ICs, but there's a significant difference in performance that is very easily audible. It is what makes a majority of the difference between the D1 and D2, the ground wire does make a difference, but it is much more subtle than the connectors, and the UPOCC ground wire is about 15x the price vs the mil spec wire on the D1s.
So I'd prefer to make sure the D1 level XLR has the same performance as the single ended D1 before getting into using more expensive parts. If it turns out Neutrik is as good as it gets for XLRs than I will be a very happy guy, but it's not likely.

You also have to understand that this isn't exactly replacing my day job, not even close. I make an reasonable hourly rate doing this, but no "profit". The cables I'm selling would be about $500 for the D1 and $1500 or so for the D2 using typical industry markups for this product. My goal is to offer a
much better value for the money than anyone else selling cables... and my cables won't be embarrassed when compared to any cable out there regardless of price, even the D1. These are top of the line cables at much lower prices than anyone else is offering.