Ok, I would go for that design.

Will your track allow a custom hardcase 4s lipo? For example. Bending a peice of thick lexan into the correct dimensions to cover the whole pack then shrinking it with specs on the shrink. For budget purposes that sounds like your best bet if your track will allow it.

Why? His track allows soft shell lipos.

my track doesnt even require hard cased lipos

I beat you.

Bleh.

Found out that the track runs 5 minute heats and 15 minute mains. So I should be able to use my zippy for the heats and whatever other battery for the main

Why not get some low-mah lightweight batts for the 5min races?

Depends on how much I have in my wallet..:whistle:

id try and run the same voltage in both the heats and mainsgoing from 5s to 4s allt eh time would screw with your driving and be a pita to change the cutoff everytime....

maybe mike could chime in i know he has alot more batts availbe to him than what he has listed he may can get you pair of 3300 or 3500 4s packs. his new lipos are top notch.

I just sent him an email:yes:

im sure he can find something good for ya in the 4s 6000 - 8000 range and alot of the packs he can get are short in length which is what you need to put them both behind the spur gear/ centerdiff, if you really want the hot setup you could have him make you a couple custom size tray matching trays to run on each side in the back, would be a very nice setup and ultra secure.

Maybe this will help some. http://www.rc-monster.com/forum/showthread.php?t=16216 Maybe not.

Ok, how about some cheap ebay batteries? Check these out, I'll get you a link in a sec.

I shot him an email to see what he says. 6200mah should get me through a 15min main without dumping, i want to know how they are getting 30 minute runtimes out of comparable packs. I still dont know what voltage to run... Length is not a problem, Matrix is a good 3/4'' longer then most truggies- even my zippy can fit behind the spur without a problem
It did help a lot but the difference between what people are saying makes me iffy. Since no one runs the same setup you know:oops:

I misread what youve asked but IMO it wouldnt be bad to take the extra step to protect your packs...