EverEdge and Indian sandstone - pointing issues?

[Wakey]

Hi - I've recently finished laying 28sqm of riven Indian Sandstone (Westminster Stone's 'Antique Glendale' - tumbled finish, calibrated to 22mm thick, 4 sizes). First time I've laid stone paving, so I read pretty much everything on this website, including all(!) of this forum, and constructed it as follows:

Sub-base: 80-120mm MOT Type 1 hardcore (compacted depth, depending on the amount of topsoil I needed to remove to reach a firm sub-grade)
Bedding (laying course): full bed of 6:1 sharp sand and cement mortar, wet mix, no plasticiser, 35-50mm thick
Bond bridge: Sika SBR+ and water at 1:1, cement added to make a slurry - applied to the back of each flag
Pointing: a 4:1 building sand and cement mortar, 'damp' mix - packed in firmly and finished (smooth, flat and slightly recessed) with a 10mm tuck pointer (majority of joints are 9-15mm. There are a couple at 7mm and one at 25mm...)

I'm very happy with the end result (and braced for the comments...), so many thanks to Tony and everyone who has contributed to this extraordinary website - I consider myself a competent DIYer, but I wouldn't have even contemplated starting the paving without all of the knowledge given freely here.

Now for the metal edging... I have 45m of Corten steel EverEdge Classic (45 x 1m lengths of 125mm high/1.6mm thick edging, with 94mm long spikes) that's been weathered whilst I've been destroying the garden, so it's now got the orangey-brown 'rusty' coating. This will form the edging around the paving (as well as between a chamomile lawn and a long plant bed), with approx. 95mm of the 125mm face showing and forming an 'upstand' to retain raised beds. And I've made my life infinitely more difficult by having a stepped/staggered edge to the paving, so there are loads of right-angle bends in the edging...

My installation method for the EverEdge is:
Chop back any excess bedding mortar and sub-base, down to approx. 125mm depth, to allow installation of the edging approx. 15-20mm from the edge of the paving;
Mix concrete 3:3:1 - moist mix of ballast (20mm), sharp sand, cement (I could have used a leaner mix, but I have the materials and I hope it will be about the same level of permeability as the bedding mortar);
Create haunch - bed the whole depth of the spikes and approx. 10mm of the bottom edge of the Everedge into the concrete, then haunch up approx 40-50mm at the back. In this way, I have a 15-20mm wide x 20mm deep channel between the paving and the front of the EverEdge that I can point to match the rest of the paving. When the soil is added and banked up at the back, there should be very little flex in any part of the face of the EverEdge.

I was happy that this was a sound technique, based on the couple of pieces of information I spotted around the website:
"EverEdge... An edging system such as this has so many other potential uses: it could be set into concrete to give an 'invisible' retainer edge for block paving, tarmac, resin-based surfacing, or almost any other form of hard paving."
"There will be other circumstances where it is advisable to install the Core Edge system into a bed of concrete and haunch with the same. The most obvious applications are for pavement restraint where the planned surface is heavier than normal, or may carry vehicular traffic. Core Edge used as a very discreet retainer for block paving is a typical example..."

And then... I realised that all of the illustrated examples on this website - and 99% of the photos on the internet - show the edging installed so that the top edge is flush with the paving (none of the face of the edging showing) and/or with a loose material (pea shingle, gravel, slate chippings...) between the edging and the stone paving.

Does this mean that I can use a traditional mortar (as above) to point between the stone and the EverEdge, or will it quickly become loose and disappear over the coming months...?

Since I'd already installed 5m of the EverEdge, I wanted some reassurance - I spoke to Simon Arrowsmith at EverEdge and he was happy that my technique would be sufficiently robust to ensure a decent lifespan for the mortar.

I was hoping to hear from anyone who has installed a metal edging product in the same way as I've described (at massive length...!) - are there any issues I haven't yet considered in my installation method, and what sort of lifespan/performance can I expect from the pointing?

Thanks for reading this far! I look forward to the constructive criticism/piss-taking...

[Wakey]

Evening, all - should I assume from the deafening silence that no-one has done this before? Or it has been done before and it’s doomed? Or has no-one managed to read right to the end of my post...?
Thanks in advance.