I don't think its a problem if you beef things up a bit. Here's the rules for Nostalgia. The key statement is that the changes don't "significantly change the performance or appearance of the model as it was originally designed".
Go for it!!!
5.1. Modifications: No modifications to the original design are permitted, except as listed below. Any modifications other than those listed in section 5.2 which, in the opinion of the event director, significantly change the appearance or performance of the model as it was originally designed, shall not be permitted. This prohibition includes, but is not limited to, changes in airfoil, changes in dimensions, and use of moveable control surfaces not included on the original design.
5.2. Allowable Modifications:
5.2.1. Landing gear may be changed in length or material, but must exit the model at the original position. A tail wheel may be substituted for a skid and vice versa. Wheels may be of any diameter.
5.2.2. Leadout position may be changed from that shown on the plan. Ground-adjustable leadouts are permitted.
5.2.3. Control travel, control mechanism location, and control mechanism may be changed.
5.2.4. Tip weight may be changed or may be adjustable.
5.2.5. Tail hook and its location may be changed.
5.2.6. Structural changes to strengthen the aircraft are permitted.
5.2.7. Building and finishing material substitutions are permitted.
5.2.8. Location of access hatches may be changed.
5.2.9. Engine mountings may be changed, and engines of different displacement may be used.gia and they allow for changing the original design as long as it keeps to the "original" performance.