Harness design with bulkhead/breakout panel

Hi all. I am almost done with the professional level course and I am in the early stages of planning my harness out.

I am designing my harness to route through a factory electrical bulkhead panel for serviceability - this way I can quickly disconnect the entire engine-side harness with only a few connectors, any time I need access to that area and/or if the engine has to come out. The bulkhead is very close to where the components are so all leads after the bulkhead will be pretty short and it should be easy to install in a tidy, organized way and dramatically minimize the number of branch points in the engine bay.

I have a few questions about the best way to approach this:

1) For shielded leads (cam/crank/knock/etc), I will have to pass the shield through the relevant connectors. I know I can pass a single shield through on a pin, but what about multiple shields? I have enough pins to run each shield through its own pin, but I'm wondering if it's possible to reduce the pin consumption by using a single lead for this. What would be the downside of running a separate lead through the pin for the "engine side" all the way back along the harness to the ECU pin for the shield grounds (effectively making two different shielded sections, one with a longer lead back to the ECU that would splice in at the connector)? I am assuming that merging all of the shield leads together into one pin and then breaking them out again will have a bad effect on the shielding's effectiveness so I am not planning on trying that.

2) I have numerous breakout subharnesses with their own bulkhead connectors for ease of maintenance. Does it make sense to re-join these into a new run of concentric twisted harness? I was planning to have the engine bay leads break out at the panel which will reduce the number of branch points, but I'm wondering what the experts think of that - is there a benefit to breaking them out and re-inserting them into a new bundle after the bulkheads, vs just having each lead go directly to where it's needed and accepting that there will be at least a few parallel leads that aren't nicely bundled together? Apart from appearance, I can't think of a compelling benefit to making a new run of concentric twist after the connectors. I do anticipate that I will need to remove some of the sub-leads for ease of access (the engine wiring is in a very cramped location) so I am okay sacrificing appearance for ease of maintenance.

3) Regarding regulated sensor voltage supply and sensor ground pins, I know the course says to ideally have one splice right at the ECU and run a lead for each branch, but I am hoping to reduce the pin count in the connectors and simplify things by having my "one splice" after the bulkhead - running one long lead each from the ECU +5V and sensor ground pins to the bulkhead, then having the splice in the boot directly after the bulkhead. Is there any major downside to doing this? I have a lot of sensor leads going to the engine and it would be much cleaner and simpler to eliminate the bulk of those leads from the harness, but I don't know if I would be shooting myself in the foot.

4) Since I will have one very complex multi-lead branch on the inside of the bulkhead, I'm worried about the weight of the harness putting strain on the connectors. Would it be worthwhile to install a support bar directly behind the bulkhead connectors? I am thinking of bending up a steel bar and welding it to the rear of the bulkhead panel, and using that to secure each lead with cable ties. However, I'm not sure if this would be overkill.

Thank you!

1) If I had the pins, I would keep a separate shield pins for in shielded cable. If the distance to the ECU was short on the one side, then I might consider combining all the shields together and grounding at the ECU side of the bulkhead.

2) Do what looks neat, and/or is less work.

3) I normally do all the splicing for sensor power/grounds at the bulkhead connector. Saves pins, make the ECU/bulkhead harnesses simpler / smaller.

4) Harnesses usually have enough strength to stand on their own, but if you want to make a support go for it. Just leave enough room to work on / remove the connector if necessary.

Thanks, David. The ECU side of the harness is actually the largest portion of the total length, it'll be 5-6 feet or so. That's why I think the only options are either two separate lengths of shield, or pin each one out. I'll most likely just pin each one out separately, even with my last minute documentation changes I still have 2-3 open pins on my desired connector.