I made a similar choice by building the battery holder myself. First of all I checked the CG to see where it would fall and now I can move the batteries back and forth 5-6 cm, plus they are super easy to insert. I made a quick video to show the various solutions inside the fuselage. Finally, I covered everything with a plate covered with faux carbon film.
Some items used:
Torcman NT530-35-Z | 14 Pol | 14 W | FES | KV218
RFM 18,5 x 12 CFK white
Offset clamping middle part 41/8/8
Y-Spant | Motoradapter | LK35 | RS-LK59/71 | NT530
Ringspant | Montagespant | LK71 | 90x105x4mm
FES Ex | UNI8 | POSTIOINIER-DISC IBEX
Ibex 130A Brushless Controller
IBEX Hallsensor
IBEX Temperatursensor ID
HEPF USB Interface
Propgummi | UNI8 | MittelstĂŒck gekröpft | MittelstĂŒck 40mm
UNILIGHT STROBE-Large lighting set 3S Lipo (12V) 24Watt