Replacement instruments in panel above companionway in IP380

I am trying to replace the tired ST60+ gauges located in an enclosure located above the companionway in my IP380.  The new I50 and i60 gauges are of the same size, but need to be connected to a Raymarine backbone cable.  The old Seatalk and transducer cables arrive in a bundle from the instrument panel, running between the cabin roof and the headlining, which appears very solidly built-in.  I have tried putting a cable puller down from the instrument panel but without success.  Has anyone managed to do this?  It looks like I could pull the bundle out from below, with a mousing string attached, but I am not confident it would go back upwards with the additional cable!
Any thoughts would be welcome.
Many thanks
Paul
 

I do not know the internals of the 380. But, on my IP37 (1997) I upgraded my electronics which required running cables through a very congested and tight entry under the helm. What I found works is (1) a 1/8th inch stainless leader for cable pulling. (2) coat any cables you intend to pull with Baby Powder to reduce sticking and friction. If it is possible to attach two cable leaders (see 1 above) to a single cable instead of the bundle and then use point 2 you may have success with the backbone and the original cable into this space (which incidentally I had to add so my older ST60s could talk to the newer SeatalkNG High Speed network for Axiom+ MFDs). Good luck. Mac