I am 6'4" and a good bit more than 100kg too! I am currently using a cheap Covacure hammock with a OneTigris underblanket and it seems comfortable enough. I have a Jura 2 XL too but its been a bit warm recently to try it out, so I've just been using an army issue wool blanket. I am considering the DD XL Frontline but I've held back as I'm not sure if my 3m x 3m DD Tarp will cover it in a diamond setup and if I will still be able to use my underquilt which is 280 x 120cm, even if it restricts a diagonal lay.
What are your thoughts after owning the Frontline XL?
As it happens I am typing this reply while having a cup of tea next to my hammock after another test night! What great fun.
First up, I use the DD 4x4 tarp as I like that extra cover. I think it would be a bit tight with a 3x3 but the diamond formation would probably cover it, but it depends how "protected" you like to be.
The Frontline XL has been outstanding so far and I am pleased with how easy it is to use and it is comfortable for my dimensions!
But you're on to something about the underquilt. It is one part I do not quite have sorted yet. I am using the DD underquilt and I have it biased towards my head end. It does work but I also need to bias it to the right side at the head end to make sure my right shoulder is covered as the quilt wants to keep returning to the central position. I plan to fix this by changing the bungee in that corner with a short fixed line. That will be the subject of the next test night.
I hope that some of all that helps you in some way.
Happy hammocking mate.