ok some people that post here really need to learn a bit and read a bit... its like some of you guys only read the first post and the lastone,
1/2" is sufficient for 30"tall, of corse he is going to frame it it... GE1 is the most popular sillicone for tanks, GE2 being also popular. and all you have to watch out for is it saying that it contains the fungiside it doesnt have to say that it doesnt contain it.
and like you said. take it apart. sillicone is chraper then the stress of trying to find a tank for your fish and bucket/towels...
that seam really doesnt like like it would last. with a good braveing it would hold, for a while but not long...
Just make sure to over do the bracing on the top. remember its the sillicone between the glass that holds it together not the sillicone in the corner.
Looks like its going to be BAD!!! let me guess... freshwater rays?
also since your doing it over again have you thought of useing black??? i mean to use it on every tank i make but i always seem to have clear laying around. i made one with black and it looks good... if you ever get ich it wont turn blue/green on you. also it lasts longer with a broud spectrume light...