Scaling loaded meshes

Hello, I’m am creating a class that inherits from of3DPrimitive and get the mesh by loading an .obj file.

Something like:

#ifndef STAIRS_H
#define STAIRS_H

#include "ofMain.h"
#include "ofxAssimpModelLoader.h"
#include "MeshHelper.hpp"

class Stairs : public of3dPrimitive{
public:
    Stairs();
    ofxAssimpModelLoader model;
};

#endif // STAIRS_H

Stairs::Stairs(){
    model.loadModel("stairs.obj");

    getMesh().clear();
    getMesh().append(model.getMesh(0));
    getMesh().enableColors();
    getMesh().enableNormals();
}

But the sise of the model it is too small. I have tried to scale the model before getting the mesh, but it does not work.

#include "Stairs.h"

Stairs::Stairs(){
    model.setScaleNormalization(false);
    model.loadModel("stairs.obj");
    auto bbox = MeshHelper::getBoundingBox(model.getMesh(0));
    float originalXSide = bbox.max.x - bbox.min.x;
    float side = 100;
    float scaleRatio = side/originalXSide;

    model.setScale(scaleRatio,scaleRatio,scaleRatio);
    model.update();

    getMesh().clear();
    getMesh().append(model.getMesh(0));
    auto bbox1 = MeshHelper::getBoundingBox(model.getMesh(0));
    getMesh().enableColors();
    getMesh().enableNormals();
}

or, it does not scale the mesh. if you call model->drawFaces(), the model it is scaled, but if you call model.getMesh.draw(), or in my case, stairs.draw(), it draws a mesh with the original dimension.

I had a look to the ofMesh class and there is no scale method. So, I think that the only way that I have to scale a mesh is to assume that all the vertices are relative to a centroid, and multiply all the vertices by a scalar. Am I correct that this is, at the moment, the only way to scale a mesh?

glm::vec3 scaleCenter;// set this to the point around which you want to scale.
float scaleFactor = 0.5;
for(auto&v: model.getMesh()){
    v = (v - scaleCenter)*scaleFactor + scaleCenter;
}

I have not tested this code. Just wrote it from the top of my head. But I think it should work.
Hope this helps.
cheers.