Ditto.
The only times I have used other than the stock Sanyo flat packs was a custom 600AE pack I made to fit in the nose of a Mini Blade slope glider, a tiny 270mAh pack in a kit built Hyperbee, and a 1500mAh Batteries America pack for a Super Scooter slope combat plane. Needed the ballast for that last plane and figured that a bigger batt pack would be the ticket.
All my glow planes other than the Hyperbee use the standard flat packs.