How much difference do lower mass cartridge clips make in playback?

I can suppose no reason why a "low mass" clip would improve sound (rather the opposite).I like the Mitchell clips better than the Cardas. See if you can stick a round toothpick in the loose clip and squeeze carefully with small pliers to regain tension.

I did that several times, hence I believe it's broken.

Thanks to all who responded. I have some JA Mitchell silvers’ on a wire loom I made for my ET 2.5 years ago. I may remove them and replace to my 3d arm. Years ago, in searching for the shortest length clips I ran across the Clearaudio clips. I bought them purposefully to use with my Acutex 420 STR on my tt project, as the pins protrude at a steep upward angle making the normal length clips impossible to use and feel good about it.

slaw&oldears, for those who never owned Mitchell clips will be
difficult to understand what you are talking about. Using an thing 
and talking about or describing the thing are different issues.
Because Mitchell clips are made from silver which is an soft
material one can't get ''tension'' back by ''squeezing'' its ''legs''. 
The tension is lost by using different carts with different pin's
dimensions. The added problem is the difference of ''thickness'' 
by headshell pins and cart pins. It is a shame that  there are
no standards  for such basic dimensions. For such expensive
items one should not need ''toothpick''  as fixing ''instrument''.

+1 nandric