With low pressure ratio combustors they certainly need to be larger , combustors are compared by their "combustion intensity " .....BTU's / cubic foot/atmosphere/hour , so if the "atmospheres" ie pressure , is low , then the cubic feet need to be greater to compensate .
The engine shouldn't run any "hotter" , the ultimate temperature will depend on what the turbine wheel can survive , but what will be "relatively" hotter is the exhaust due to there being a small pressure ratio across the turb stage and jet nozzle resulting in less temperature drop occuring for the same TIT as a higher pressure ratio engine , .................less pressure/temp drop means less power
OT , .................LOL.....with a compressor sucking >200 hp from the turbine , an extra hp or 2 for brass bushes and thrust bearing , is kinda irrelevant ...............balls at high rpm create a lot of drag , so theres not such a big difference between them and "brass" , balls are best at those lower initial spoolup rpm , thats why they're better on performance automotive turbos where you want every last millisecond of turbo lag to be eliminate, but for us , we're idling at a decent "boost" , so that advantage the balls have is negated to a large extent .
Cheers
John
....