i've always used flat top batteries in my grand and i use a magnet on top - not a weedy little Reo door magnet, but a really sticky neo from K&J Magnetics. As a lung-burning button masher, i have used this arrangement for about 4 years and i also modified the fire button by using a rivet head epoxied to the bottom of it to stop it melting!
Naturally, none of this is recommended practice, but if you buy reputable batteries and care for them, then you can really get some great performance. There is even a mod for a Reo that Custom Classic does, so you dispense with the spring entirely and use a solid silver bolt
i use 30A batteries, so the mAh is lower than a lot of the others 2200 usually. So they don't last long at full blast - but i can get a work day easily from them. i use 3mm RxW and a 0.3Ω Clapton.
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