The glass filled nylon mounts that ship in the 4*60 kit (not sure if the same are in the ARF... I expect they are...) are GREAT!

Very sturdy and plenty long for up to a .91 4-stroke with ease. There is no good reason to get different mounts. I used a O.S. .91 FS (4-stroke) and 14X6 APC on my 4*60, which I put retracts in. A bit more power than needed. but it was the best engine I had for the aircraft. (My .60 2-strokes are getting old and unreliable not a great plan to keep using them. I don't have a .72 4-stroke.)

The only real problem with the individural beans by Sig... you have to be good at getting the holes straight. There's a trick that works EVERY time.

Bolt the engine to one rail... bolt the other (undrilled) rail to the model. (not having drilled the firewall for the second mount.)

Clamp the engine mounting flange to the secnd mounting rail with a Vce-grip (use a piece of wood to prevent maring the mounging lug)

Mark the firewall for the second engine mount.

Drill the firewall and bolt the mount n place. Now you can mark the other rail... pull the engine clear to drill and everything will line up perfectly.

You can do this before putting the firewall into the aircraft... or after the model is built. (but its harder to get the blind nuts in after the 4*60 is built)