Tamiya Boomerang, Super Sabre LiPo brick pack battery holder

I really wanted to run the common brick lipo batteries in my vintage Tamiya Super Sabre runner so I needed to come up with something to make them fit. The original holder wasn't long enough for a lipo brick pack (but would take the right size lipo stick - like a CoreRC one - I don't have any of those though!). Plus the dusty track I run on also made pulling the battery door pin out a real challenge as it always got stuck in with fine particles of dirt - so I wanted a slide-in method to get the b