Singlespeed & Fixed Gear - loose spider

i recently put an fsa carbon isis drive compact crankset w/ a 34t chainring on my fixie. it has a carbon spider, which i discovered was actually loose. we were able to tighten it by putting the lockring in a vise, clamping it to the table, and attaching a very very long pipe to the crankarm and turning while i put my full body weight on the center of the crank. it tightened quite a bit, to the point where the vise started rotating, and my friend said it was getting a little hard. we put around 60 n/m of force into it, which is what it says on the back of the lockring. i can ride it well now, but the spider still slips when i jump on the pedals really hard. i really dont think i should tighten it anymore unless i want to risk breaking it. so am i correct to surmise that these cranks are just not meant for fixed gears? or is there something wrong with the crank?

fsa carbon spiders don't like skippin,skiddin,etc.

am i correct to surmise that these cranks are just not meant for fixed gears? or is there something wrong with the crank?

I don't think they had backpressure in mind when they built that crank. Also, with a 34t ring, you're probably running a pretty low gear, which increases the stress on the spider.
Solution- new crank.

so am i correct to surmise that these cranks are just not meant for fixed gears?

You are incorrect. They are meant specifically for track bikes which are fixed gears.

Also, with a 34t ring, you're probably running a pretty low gear, which increases the stress on the spider.

INCORRECT.

On the upside, you now have a nice carbon fiber paperweight.

On the upside, you now have a nice carbon fiber paperweight.

he might be able to get a replacement he could then then sell to someone who has an actual use for it.