Harvia Chimney install- how many bends is too many??

Hi Everyone-

Im just about to install my harvia m3 wood burner. I bought the harvia 90 degree bend section with it, planning to send the flue out the wall and up, so having 2 90 degree bends (with a protected twinwall section through the wall).

Our local chimney fitter came to have a a look, and reckoned that having 2 90 degree bends is too much, preferring two 45 degree bends to pass it through the wall, and having more draw for airflow.

I see that Huum sell a 'through wall' kit, which has 2 90 bends in it. What are peoples experiences of this type of chimney? Is there enough draw, without having a really tall chimney? can wood fired sauna heaters be any different to household burners in this regard?

https://preview.redd.it/2ltq79vfeegf1.jpg?width=416&format=pjpg&auto=webp&s=97f7dc513f013bcee4754233b791fa92e65a5ee3

thanks all!