Future accretion models need to be calculated with a fully self-consistent treatment of the stellar mass-radius relation to investigate this aspect. The McKee & Tan (2003) models, in which the stars accrete at rates significantly above $\sim$10$^{-4}$ , implement an approximate treatment of the the Palla & Stahler (1992) results and their stars join the main sequence at masses of around 20 M as expected. However, their radii never get above the 15 R for Palla & Stahler’s $\sim$10$^{-4}$  case suggesting that these have been under-estimated for the highest accretion rates. The Behrend & Maeder (2001) mass-radius relation shows a similar pattern of swelling towards larger radii, but again not as much as one would expect based on Figure \[fig:palla\], since their accretion rates exceed $\sim$10$^{-3}$   through the relevant mass range.

Nakano et al. (2000) used a polytropic model to estimate that a young star accreting at $\sim$10$^{-2}$  would have a maximum radius of about 30 R. In a different context Kippenhahn & Meyer-Hofmeister (1977) calculated the affect on the radii of stars already fully on the main sequence of accretion at rates exactly in the $\sim$10$^{-4}$  to $\sim$10$^{-2}$  range of interest here. They found that the stars can expand 