95% of the racers out would never feel the difference between a matched and an unmatched pack. Unless there was a bad cell, the voltage from the unmatched pack would probably be within 1% of the voltage of a matched pack.
The main advantage I see with matched packs is the fact that all of the cells charge and discharge at a similar rate. This just keeps individual cells from failing due to charging and discharging at the extreme rates we use.
The second advantage of matched packs is the ability to see the the labels and know what you are buying. This way, if you are willing to pay the extra money for a matched pack, you can decide if that specific pack is worth the price.
On the spec 1500 batteries, I didn't charge them at 7 amps. That is just asking for trouble. I usually charged them at 5 amps with a .03 cutoff. Since they are unmatched and in a stick pack, it is impossible to maintain them properly. They are made of NiCD cells, so memory and heat are their enemy. You can only discharge them to 5.4 volts and hope for the best. With these old NiCD cells, traying is critical to long life of a pack.
Our track recently legalized the new Spec battery from Trinity. I believe the cells are GP 1800's. The track owner put a couple of packs through some pretty abusive tests to see if it held voltage better than the DynaFun packs. After a month of this, he deemed them legal. They are a little more expensive ($20 vs $14) but their longer life will make them cheaper in the long run.
Jeff Gilligan