How to create a wide route with coaxial shielding in Innovus?

Dear community

I have a design containing two IP blocks which are connected with "critical high-voltage" nets. According to the datasheet, these nets need to be routed with a trace that is at least as wide as the corresponding pin (1.46 microns in this case) and coaxial shielding, that is, an additional trace towards ground placed to the left and right as well as a shield on top and bottom. The shielding can be minimum width with minimum spacing.

I create a non-default rule for the wider trace as follows:

Innovus > add_ndr -width {MET1 1.46 MET2 1.46 MET3 1.46 MET4 1.46 MET5 1.46 METTP 1.46 } -name 1_46w1s

The only way to assign shielding I could find in the manual is with nano route. Thus I set

Innovus > setAttribute -net myNet -shield_net vssd
Innovus > setAttribute -net myNet -non_default_rule 1_46w1s

Next, I run global and detailed route:

Innovus > selectNet myNet
Innovus > setNanoRouteMode -quiet -routeSelectedNetOnly 1
Innovus > routeDesign -globalDetail

This does not yield the wanted output yet.

Problem 1

This only creates a shield to the left and right of the net, but not at the top or bottom. There are three valid solutions:

1. Create the net on MET2/MET3 and place a shield on MET1/MET4
2. Create the net on MET1/MET2 and place a shield on MET3 only
3. Create the net on MET3/MET4 and place a shield on MET2 only (MET5 and MET6 are exclusively used for power routing only, i.e. there already is a "shield" on MET5)

How can I configure Innovus to create coaxial shielding according to the valid scenarios above?

Problem 2

Nano Route correctly uses the non-defailt rule to place a wider trace. However, sometimes the shield is not placed at all. I assume that Nano Route has some internal roules where it decides whether the shield can be placed or not. The problem here is that I actually need to run the Place and Early Global Route command before I am able to run Nano Route. As a result, there might be other nets routed nearby, thereby taking away the space that is needed to place a shield - at least that's what I believe is happening. Maybe a routing blockage would help here as a workaround. However, I would actually prefer to route those critical nets even before the placement step and then somehow lock them. Is there a way to manually place routes without relying on the Nano Route command?

Problem 3

Whenever Innovus performs a layer change on said critical net, only a single via is placed. How can I tell the tool to place as many vias as possible?

Thank you for any help.