>>3555
Going to give you the short and sweet. There are no 40Amp CDR batteries on the market. Brands like Trustfire/Efest/Etc are rewrapped rejected cells from bigger companies. LG/Sony/Samsung/Etc.
Now the problem is, using a regulated device can change the actual amount taken from the battery. If it's parallel, you'll have at least 40 amps from the dual vtc4s. If the mod is wired in series, you have a higher voltage, which will also cut down on your actual discharge rate.
Also VTC4 & 5s are better off as 20A CDR batteries. The VTC3 is a 30A battery. With the higher mah rating, the lower your actual Amp discharge is.
The LG HB6 batteries are true 30A cdr that can be run up to 40A, but will get quite hot. It's only 1500mah, but like I said. Shorter mah is a higher CDR.
You should generally be fine. If you feel like being extra cautious, definitely get the LG HB6 for $4 each on illumn or get the VTC3 for whatever it costs.