Well said BEagle!
Your turn radius will depend on a couple of things, wind being one - speed another. The faster you are moving the bigger the turn so even if the chart was to scale you would never 'overlay' the diagram exactly unless you were spot on the speed assumed on the chart (assuming 0 wind). Dont forget as well that you are speed limited dependant upon the holding altitude (<6'=200kts , <14'=230kts , 14'+=265Kts - Off the top of my head so someone correct me if I am wrong). If you have a xwind during the hold then although you can adjust your legs to meet timing requirements (assuming a 4min pattern) but you won't fly a perfect oval (more like a keyhole) as during the procedure turns you will pushed out on one turn and tightened in on the other due to the effects of the wind.
The main thing to worry about is making sure you stay on the protected side of the hold or procedure turn and dont stray into the unprotected side as it may be for terrain clearance and you wont get a second chance then!!!
Complete the procedure turn at the time required (or within the specified distance required if flying something such a backcourse localiser approach), stay on the protected side and get on the inbound track as Beagle says.