I think rather than seeking expert opinion, we need to know what actual evidence the ramp theory is based on. If we're talking about a bit of compacted chalk in a hole, there can be many alternative explanations. The only evidence that would worry us would be something that could not possibly be explained in any other way. There is nearly always room for doubt and that's all we need. If ramps were used then where did all the chalk come from? Such a large quantity of material would surely have left evidence of big pit nearby, which they would have refilled afterwards with the debris. Wouldn't geophys have found this?

As I said before, if the evidence for ramps is overwhelming then I think we should stay well clear and stick to stone rowing.

You mentioned one large ramp for two uprights or two smaller ramps from opposite sides. I don't think the hole profiles would support the idea of opposing ramps.

I think what appear to be ramps are just slopes cut to allow the stone to pivot smoothly into its hole. The profile as shown on the BBC drawings is ideal for such a purpose.