Replacing boot brake light - nuts how tight??

[JSz4]

I replaced my cracked boot brake light last weekend and made sure I ordered the new bolts and weaker springs to avoid it breaking again.

However I just wanted to check how tight I should do the nuts up. I have done them up this far however the corners of the brake light do not appear flush yet.





I have read that you should keep doing it up by hand until you can't and then half a turn or so with a spanner/wrench. I can't fit my hand in there so have just been using a socket/extension bar but tightening by hand, not using a wrench. However, with the softer springs it feels like I can just keep tightening until there is no more thread left and the spring is fully compressed, is it safe to do this or is it likely to crack the light?

Thanks

 

[enuff_zed]

I found it to be trial and error, though I never really bothered with any weaker springs.
I just nipped them all up until they felt about right, then noticed the ends were sticking out.
So I backed off the centre nut a half turn and tightened the end ones half a turn. Did this a few times until it started to take the curve.
After a week or two I repeated the exercise as it had all settled a bit.
Also worth parking it tail to the sun all day and doing it when the plastic is warmer.