I've been tying for freshwater stuff with double mono weed guards this year. I haven't liked the single loops because after a period of time stuck in a fly box the mono takes a set and the point is sticking out to catch weeds.
What I do is take a 6-8" piece of 20-30 # maxima and flatten both ends with pliers. Wrap thread ~ 1/3 of the way down the hook bend. The flattened ends of the mono get tied down, 1 per side, on the side of the hook bend, with the mono forming a loop between the sides. Add zap a gap to seal the threads as needed. Push the loop out of the way & tie the fly.
Leave a little space at the head of fly to tie in the weedguard. When you are finished tying the fly pull one side of the mono forward and size the weed guard. Flatten the mono at the tie in point. Pull the mono loop taught and flatten the second piece of mono at the same location as the first. Tie them both in and tug on the loop to make any minor adjustments.
It took far longer to type or read this than it takes to make the loops this way. I'll take a picture of a fly with a weed guard tied this way this tomorrow if your interested Marvin.