The road to success is always under construction.
I made long soft shackles with the same lash-it and put a couple extra wraps on a Klemheist. You don't need any hardware this way.
I splice continuous loops or soft shackles out of 1.2 mm Tech Line from DIY Gear Supply, then prussik them on a tarp ridgeline made from 1.9 mm Tech Line. DIY Gear Supply says that the 1.2 mm line is "not recommended for splicing projects." But I haven't had any trouble splicing it.
The Tech Line prussiks might slip a bit when they are new, but they grip better once they are broken in. I find that they grip fine with 3-4 wraps. For whatever reason, I have never been able to make klemheists work.
Good option Mouseskowitz, I hadn't thought of that. I've only used klemheists as prusik replacements for webbing. All I care is that my loop holds under load and cleans w/o fuss. I'll of course give both a try.