Lost stability , why ?

[Freefallin66 0]

Used different rig than my normal student rig and it had straps on the sides that myself nor my instructors were aware of - they were never tightened but you can't tell because of the weight of the container walking or sitting but in free fall it was very easy to feel. This caused a space between my back and the rear of the container and in free fall felt very loose. My cutaway was more to my side then my front , same with my reserve D ring and my chest strap very high after deployment.
Here's my thing though - I jumped category D jump 1 with one instructor who released me just after stabilization at about 13k or so - I remained in a stable arched position ( I've been a stable student since category B and have two hours tunnel time so I'm comfortable with the arch , relaxation , legs and turns etc ).
My first command was 90 to the right and I began by checking altitude looking to the right then starting my turn. My body turned quicker than normal , something felt different. I continued to turn unable to correct or even stop the turn - I sped up quickly, ultimately losing total control of all axis. I could not see my altimeter nor could I get to my hackey. I spotted the ground a few times but had no clue what my altitude was. I immediately went back to my training from previous instructors and wind tunnel instructors. I flipped myself back over from back down position but my body continued to turn and flip. I went directly into a deep arch with arms out and legs spread a bit but down and relaxed ... almost an X position. No luck at all - I couldn't control my fall nor could I get to my hackey -
I never got totally stable but continued to attempt reaching my hackey - I finally got my hand on it and held onto it with a thousand foot pounds I'm sure lol - out it went , deployment then of course a line twist. I was just under 3k feet. I was still in some kind of sensory or shock thing lol so my landing sucked and it was on the edge of the runway.
I'd love some input on this one if you have the time. Tenured instructors are very welcome to leave comments but all opinions will be appreciated.

John White , RCDD

" Those who don't read have no advantage over those who can't "

[riggerrob 558]

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Sounds like a loose harness.
Time to ask local instructors for a lesson on how to adjust your own harness.
As for not noticing lateral looseness on the ground: shift the container high up your back to eliminate slack ... before tightening leg straps or lateral straps. Some lateral straps require a second person to help you adjust them.
Shifting slack up and over your shoulders will also help you correctly adjust your chest strap so that it remains at chest level throughout the skydive.

[sammielu 3]

Yep, loose harness/rig too big for your body. The instructor who jumped with you will have the best feeback on how you can improve. We all have to learn to fly our bodies including the rig, and a bigger rig or one that can move around on you is going to be more difficult. Talk to your instructors, see what other rigs you can jump next time, get help adjusting if the harness is adjustable.