hardtop,spec miata brackets and stress cracks ?
 

Just picked up a hardtop. My car has 600/300 xidas,1.25 hollow rb sway, fm frame rails, harddog door bars. Im considering buying spec miata hardtop brackets from rennenmetal but am concerned about putting too much stress on the hardtop and causing it to crack. Is cracking the top an issue when using the SM brackets on a car without a rollcage ?

I've been running those brackets for about a year (6 months of actual driving in the NE) without any issues. Much of the time I had 550/425 springs and drive on some horrendous roads. Just DD though; no competition.

You should be OK. The rubber weatherstripping absorbs a lot of vibration. My red car has a cage now, but PO ran it with just a roll bar for many years without issue.

I've been running for more years than I can remember with the renn brackets and a roll bar, no other braces. No cracks for me.