Yep - 2 inches in diameter and 1 inch in width is the maximum you can go.
The R is not radius, as the 15 is diameter and diameter is twice the radius!
Standard rim for an EB2 GLi was 6.0Jx14 , so you can go to 16 x 7 with no worries at all. the Classic came with 6.0Jx15 so you could possibly go 17 x 7 - but check with rego first, then insurance company on this. The rego rule in most states is 2 inches up and 1 wider than largest wheel fitted to vehicles in the same family. It's up to the interpretation of "family" by rego and insurance mobs as to what you could legally fit.
I agree with JC, as Im currently having some issues with insurance about my 17x8.5" rims at the moment. Its a technical thing that they have with how wide a rim is. I have checked with the road authorities on this and they said that as long as the overall track distance between the centre of each wheel (not offset distance) between the front wheels doesnt exceed 1592mm plus a tolerance of no more 26mm in total then its classed as being legal. It will depend on where the offset distance of the wheel is that will determine your track width.
In the same family, means any model in the EBII range. Since the EB GT was in the EBII range, it's rims are the "largest standard fitament". They had 17x8.5iirc. So technicaly it may be possable to fit 19x9.5 leagaly to EB's.
Going on this these would be the largest rims for these models
ED 18x9" (sprint had 16x8 iirc)
VX/VY 21x10" (GTS had 19x9iirc)
Remeber that you cant go more than 1" up in total roling diameter, so lower the profile as you go up in rim size.
unfortunately insurance companies dont see this as being relevant information and they have dismissed any evidence to prove otherwise. They believe that any car in its category .i.e. EBXR standard factory fitment of 15x7 wheels should not exceed 17x8 maximum regardless of other models such as EBGT.
Im with you on this daniel, but its the stupid insurance companies that make the rules in the end.