Just an idea: How about creating artificial gravity within Kharnov, that always points towards the belly of the Kharnov.
1. Make Demolisher flip on its back.
2. Carefully attach Kharnov from above.
3. Carefully lift off.
4. Enjoy your new belly mounted Demolisher
5. ??
?
6. Profit
Alternative:
1. Make Long Tom flip on its back.
2. Carefully attach Kharnov from above.
3. Carefully lift off.
4. Enjoy your new belly mounted artillery
5. Fapp you Hawkmoth D