I think your pipe will need to be cut quite a bit because of the 90 header .Start at the center of glow plug with tape measure bend around keeping the header & pipe centered. A good starting point is 8" to the fattest part of that pipe. You probally can cut the header as well but you don't want the rubber to have to bend around it will push the pipe back when it gets hot.7.5-8.5 will be optimum depending on prop ,fuel, depth of strut ect.Don't break her in too rich that it doesn't get hot , you want it to expand.Google reading glow plug it will help you find perfect needle. Then start shortening your pipe from 8" it should get higher & higher rpms until it starts to fall off in the corners pull it out just a bit.Biggeror more pitch prop longer pipe.
You can still make the pipe bracket work but I think it will have to be less wide at top, go through the gallery and see how they make them adjustable.The 440/3 might be alot of prop if it's ran too deep ,21 surface drive prop. 442-640-"642 barely" I could push subsurface with a K&B 21 on a mono.
The boat looks very nice as well.
