Hi. Very envious of the space you have in that hull! On my smaller 1:48th kit conversion I used a shaft way too long (just because I had it) but worked out OK in the end because a mini 1,600mah 7.2v battery pack fitted in just perfectly balanced over it! Never get that lucky normally!!
I agree, there seems a shortage of 35mm props for some time now as I was looking for some recently. Mine has single speed 400 c/w 20mm 2 blade "high speed" brass raboesh prop -and the hull can't really go any faster at a tad over 50% out of the water but can aerate a bit when turning. My rudders are tiny compared to yours, even after scale, I think you need at least 2 sizes down on the list there (cheap enough to replace and use the same stock sizes so no need to change the rudder tubes)!