As usual, the euro centric pre-occupation with firepower and range comes at the expense of other considerations. as the allies found in the jungles of new guinea Burma and larger islands like balikpapaan, this was a costly mistake.
Artillery in the Jungle is as important, if not more so, than in the open fields of battle of northern Europe
The Australians along the Kokoda track did entirely without artillery except for a few days from 21 September 1942. When the Japanese were on Ioribaiwa Ridge, at the limit of their advance, two 25lb guns of 14th Field Regiment were dragged up to Owers' Corner from where they were able to fire on the enemy. these were heavy guns for Jungle conditions, and this led to the eventual development of the "Baby 25 pounder." Even as redesigned the baby 25 was too heavy and immobile for the jungle.
The Japanese experience of war in China in the 1930s had taught them that in remote road-less regions the only artillery they would have was what they carried with them. On first landing in Papua they had 17 artillery pieces. These were of three types; 75mm mountain guns, 70mm infantry guns and 37mm guns which could fire an anti-tank or an anti-personnel round. All three could be taken apart and carried by horse or man. When the Japanese advanced into the Owen Stanley Range the carrying of the guns and their ammunition had to be done by men alone. One fifth of their force was needed to shoulder the burden of the disassembled guns and several thousand rounds of ammunition.
Captured Japanese 70mm howitzer, greatly coveted by the Australians and used regularly when captured
The great labour involved was, in the first half of the campaign, rewarded by victory in battle. To have no artillery, when the enemy has it, is to be disadvantaged like a boxer who finds his opponent has a much longer reach than him. The Japanese artillery had several times the range of any Australian weapon, and were muli capable, as howitzers, as direct fire guns and even with some ATG capability. this was an important facet of Japanese artillery capability....its ability to more than one job. In jungle war the gunners usually cannot see the target. This problem was solved by forward observers. These men advanced with their infantry until they could see the Australians then, by field telephone, directed the fire of their artillery on to the target.
On the last day at Isurava, six Japanese guns were engaged and at Ioribaiwa there were eight, including their three most powerful ones, 75mm mountain guns. The greatest concentration of Japanese guns during the Kokoda phase of the fighting in Papua was at Oivi-Gorari where 13 were in action. In the disaster that overtook the Japanese there, all were lost which were eagerly utilised by the advancing australians.
So, to answer the question, the preliminary question must first be answered. what are the terrain constraints that the weapon is operating. The next question is how mobile and transportable the weapon is, which includes its ability for motorised transport, and also the ability to be broken down into movable loads, when weight is a big issue. only then can we get into the argument of how much bang is the right amount.....
In the Jungle light artillery fulfils the role of medium and heavy as well, and the Japanese fielded the most versatile artillery of the war in that regard, despite its antiquated design and appearance. they had the most experience of any nation in that regard, except with the possible exceptions of the Italians and the Austrians