Too late to chime in on the investment, here, but consider this next time you invest something with a core:
Use skinny stainless steel finishing nails and penetrate your hollow wax at high smooth areas that are easy to finish later once it's cast in bronze. Leave half the nail inside the hollow area of your wax and half protruding outside the wax (like a pin cushion with a bunch of pins sticking out of it). Invest the core first. Invest the outter shell last. Once it's invested the outter shell will secure the pin heads, the inner investment (within the core) will secure the nail tips inside. Once the wax is melted out your plaster investment core is suspended nicely at multiple points and will resist any bump or jar that may cause the core to shift when moving the mold about.
Also, before you invest with the plaster, make small round BB's of wax and adhere one to each of those nail penetrations (from the outside) securing it to the finish surface of the wax. Once you've cast it in bronze you can take a pair of pliers and pull out the nails very easily which will leave the hole and a BB of bronze you can maul over and hammer near flush with the cast surface. From here you can use a TIG welder and liquify those spots and weld them to the base metal leaving a small blemish to chase and detail afterward (which is why you'd do this on areas intended to be smooth as opposed to an area where there is a lot of necessary detail). This way ALL your core pin penetrations will be welded with the exact metal the cast is made with and they will patina perfectly without showing any sign of difference in color with the rest of the piece. Or... if you don't have a TIG welder you can simply hammer the BB's over into their adjoining hole taking care to do this slowly and make the hammered fit flawless. This is how statuary was done back in the ancient times, all welding was hand hammered fit, no actual welding at all.
Also, as an added security for potential mold cracks during burn out, slide in a sleeve of chicken wire within your investment mold. Believe me... the day (if it hasn't already) will come when you go to rotate a mold fresh from the kiln to the cast area and it'll break in half from a hairline crack you didn't see. Or, during your pour the mold will break and piss bronze all over the floor. What I do is "always" include the chicken wire, then when the mold is inverted and ready to pour I slide a bigger sleeve around it and pour in dry sand to surround the plaster mold in case a pisser opens up when the melt is added which isn't all that uncommon to happen.
As for overnight curing:
You're too impatient
. I, personally, allow my investments to cure no less than 3 full days. The inner part of the investment takes longer to cure than the outter part of the shell that's exposed to the air. The dryer outer shell will wick out moisture from the inner thicker areas of the mold. Having a wetter inner shell will contribute to the vapor lock effect we talked about earlier during burnout. And as for a five day burnout, that seems excessive for a mold that size. The proper burn should run at the lower heat ranges longer so to drive moisture out rather than cause the vapor lock keeping it trapped inside. The scenario of time event I mentioned to you before would work nicely with that mold and save you some money in gas. Just offering some suggestions here is all. A five day burn may work ok but it may also cause fractures to develop in your investment. As with anything, too little or too much heat can have detrimental effect to what you're intending to happen.
