Blazt, i use the bill I will be fishing with for testing . Once I have the bait water sealed i put a tin piece of masking tape on end of bill and in install in slot. This holds well enough for testing. I also sometimes employ a temporary extended line lie that may be bent to variety of positions until a good position is found. I credit Vodkaman for this fantastic prototyping idea. My very first crank with the long bill and steep angle bill was able to swim after bending my line tie down onto the bill. On the bill as bob suggests. Many of my first baits were more learning than success.
I know literally nothing of the bait your copying or how deep it will dive. But I am developing an idea of what makes any bait dive and act the way it does. Ballast effects buoyancy and both ballast and buoyancy have influence on depth and action. So does line tie position, lure shape,lure weight, weight distribution bill angle, bill length, bill width and bill shape. Basically it can get very complicated very quick. I commend for trying to get more depth. Trying a new mod often leads to dissapointment but try and try again and finally success. My intention is to hopefully save you a couple of those tries and fast track you to success. The reason we do not see commercial baits with steep bill angles and long bills with line ties on nose is simple; they usually do not work. The buoyancy (lift) of the bait with line tie on nose coupled with long steep angled bill(drag) will nose over too far and swim out of control. There is a balance that must be achieved for proper swimming action between the two like a seasaw. Put too much force on either end of this delicate balance and no wobble. For such a large bill on a short bait with this angle, it would take so much ballast at rear of bait to balance and this would not make for a good swimmer even if it did work.
I wish you well with your build and I hope your swimming this bait soon.
Vic