all the "anti-bottoming" blocks are, is a roller placed on the rail behind the torsion spring retainer. when it gets to the roller, the spring stiffens up.
as far as anti-bottoming, it will still bottom if you are large in size and the bump, jump is large enough. in my opinion it is just a band aid for those needing stiffer springs due to weight and riding style.
at that point you will need to revalve and re-spring your shocks. the engineers can only send out a generic shock/spring package based on the majority of riders. if you are bigger than their specs, you will need to upgrade. unfortunately, sad but true.
for those wanting the blocks they can be had at your dealer for about 72.00 retail (alot cheaper than a spring and revalve upgrade). the most expensive thing in the part list is, the rollers. they are about 21.00 each. the only critical part besides the roller that you cant buy over the counter at your local hardware will be a collar for the roller. everything else is nuts, bolts and washers.
for another avenue of help, there is a guy on dootalk named bc3 he makes torsion spring spacers that slide over the upper cross shaft that the springs ride on. their premise is to keep the spring from rocking when loaded by coiling over the larger delrin spacer taking up the gap between the spring and the shaft.
i have them on my 02 zx chassis 440 and they took the place of 2 spring adjustment clicks on the spring adjuster. we also had them on the wife's rev renegade and they did the same thing there. we had to run hers in the 3rd or 4th position to get her sled not to bottom with her light weight body on it. with bc3's spacers, we ran them on 1-2 depending on conditions.
grape ape sent him dimensions for his mountain apex last year and so far he hasnt had the call to make any for the yamaha guys. i talked to him a few weeks ago wondering about the nytros, and bc3 said he still needs full closed specs on the springs to be able to machine the spacers for that particular yamaha (needs fully closed to prevent spring bind on the delrin). if guys live close to him, maybe they could take sleds over to him and help him develope this for us too. they cost the guys on dootalk about 50.00 per set. and they do work. ski
. Now I feel better 
