Since Hobby Boss copied a lot the ‘interfaces’ to other kits are good. But in case of the upper/lower hull connection they did it different to be more flexibel.
Their 2A5DK kit can be used as a conversion kit well. Not that good as the Accurate Armour one but much cheaper. The HB smoke dischargers are awful.
WIP of a LEOPARD 2A7+ QAT using Tamiya upper hull, HB lower hull and Y-Modelle converion parts:
The upper sidewalls I used from Tamiya.
The bad areas of HB LEOPARD 2 kits are mainly the upper hull anti slipp patches (far too thick), the TkCdr’s periscop (lack of detail) and the smoke dischargers of their none-A4 kits. In other aspects they are not that bad and pretty cheap.
Of course Border and RFM are in lead nowadays.
Just a senseless testfit - HB upper / Tamiya lower hull :