The fuse is required to be a maximum of 3/4" at the trailing edge of the wing. Doublers are allowed in front of that.
The one really grey area for electrics is the statement that the ENGINE is to be exposed from mount lugs to the plug. There is not plug on and electric, ( well not a glow plug anyway) It remains to be seen if I get grief over this.
As to scale, I dont know right off, but I dont recall any dimension stated for the front of the fuse thickness

Tim, smiley faces dude,, remember the smiley faces when your being a smart alec,,,
Its not so that you can remove the engine, the spec is actually in the general CL rules, and probably is more applicable to carrier, speed and scale applications where streamlining is a factor.
and this one is getting a utility finish,, no super duper stuff here,, well except maybe some panel lines airbrushed on,, or,, uh, I mean simple finish,, Certainly NOT a world class finish dude,, I mean its a profile,, just a simple profile,,
and are you calling me a nutcase? hmm I will have to remember that one,,

from the AMA competition rules for Scale
1. Model Requirements: The profile fuselage and/or engine nacelles are not to exceed one (1) inch in width except for a simulated cowl(s) which may be up to 1-1/2 inches in total width.
From carrier rules
be entered in Class II only.
3.3. Profile Class — All aircraft shall be of the profile fuselage type. Engine(s) must not be cowled in. Minimum wing area shall be 300 square inches. Models shall have a fixed landing gear consisting of at least a two-wheel main gear with at least four (4) inches separating the wheels. If a clear canopy is not used, the cockpit or canopy area must be defined with a contrasting color or color outline. It is encouraged that the plane outlines follow some type of Navy aircraft.
 
from the general rules section
Profile Fuselage Width
Class/Event      Maximum Fuselage Width Max              Width of Additional Reinforcements
1/2A Proto        ½ inch                                            3/8 inch
Scale Racing     5/8 inch                                           No limit
Slow Combat     3/8inch                                            ¾ inch
Navy Carrier      ¾ inch                                             ¾ inch
Slow Rat Racing
and Rat Racing   ¾ inch                                            No limit

and further definition

10. Profile Definition. The fuselage of a profile model resembles that of a conventional airplane in the side (profile) view and appears as a thin flat sheet in the plan (top) view. When a conventional, single cylinder, internal combustion engine is used, the engine shall be completely exposed from the centerline of the crankshaft to the top of the cylinder head when viewed perpendicular to both the crankshaft centerline and the cylinder centerline. In the case of internal combustion engine with multiple cylinders, the preceding rule shall apply to all cylinders with allowances made by the officials for appropriate mounting of the engine. No fairing may be added to the engine which violates the ―completely exposed‖ requirement of the previous sentences, and the engine cylinder shall not be contoured to present a streamlined cross section to the airflow. Additional reinforcements such as plywood nose doublers and cheek cowls or fairings are permitted within the width limits defined in the accompanying table. Such additional fuselage reinforcements may extend from the prop drive washer to a point 25 percent of the wing root chord back of the wing leading edge at the root and may be faired in. Cheek cowls used in Racing events may be of unlimited width, but may be used only on the side opposite the engine and only on models with side-mounted engines. In the case of inverted or upright engine installation, engine mounts may protrude from the fuselage sides beyond the width limitations of the table. They may extend no further aft than 25 percent of the wing root chord back of the leading edge at the root. Any such protruding engine mounts shall be of constant cross sectional shape and dimensions, without tapering. The rear portion of those mounts shall terminate in an angle of at least 45 degrees to the longitudinal axis of the fuselage unless they terminate within the wing structure. Nacelles, as used on multi-engine models are subject to the requirements of this definition.

Chris McM mentioned his experience with the Tucson (Mike Keville) 1/2A MEPS Rules reminds us that Mike did not intend that event to be an AMA (of FAI) Rulebook event. He just set up some rules for the particular thing he thought would appeal to fliers. Apparently, it works that way.

His rules grow and change every year, too. A 1" fuselage thickness has been part of it since 1/2A MEPS #1. Relaxed cowl and doubler specs? Well, if ya came to fly, chances are ye'll get a chance. Despite the relaxed specs, some very pretty and well-executed models always seem to show up. Mike's rules for the 2011 event are on the Cholla Choppers web-site and other places as well.

It's fun! (It's also fun to compete...)

Not being one to push the rules -  - I will keep every thing in the area of the motor at 1-1/2" or under with the exception of motor mount and battery.  These should fall under the realm of "it-is-what-it-is" like mufflers, fuel tanks etc. 

Thanks for the comments. It confirms, pretty much what I already knew.